Cbse Chemistry Notes for 11 and 12 Free Essays

string(34) " near to the most probable speed\." Supplementary Textual Material in Chemistry for Class XI Class XII 1 Acknowledgements CBSE ADVISORS Shri Vineet Joshi, I. A. S. We will write a custom essay sample on Cbse Chemistry Notes for 11 and 12 or any similar topic only for you Order Now , Chairman, CBSE Shri Shashi Bhushan, Director (Acad. ), CBSE CONVENOR EDITOR Prof. A. K. Bakhshi Department of Chemistry, University of Delhi. DEVELOPMENT TEAM Prof. A. K. Bakhshi Department of Chemistry, University of Delhi. Dr. Anju Srivastava Hindu College, University of Delhi. Dr. Vimal Rarh S. G. T. B. Khalsa College, University of Delhi. Dr. Geetika Bhalla Hindu College, University of Delhi. Ms. Anupama Sharma Modern School, Vasant Vihar, New Delhi. MEMBER COORDINATOR Dr. Srijata Das, Education Officer, CBSE 2 TABLE OF CONTENTS Class XI Unit 5 : States of Matter 5. 7. 1 Kinetic Energy and Molecular Speeds 5. 7. 2 Maxwell-Boltzmann distribution of molecular speeds Unit 6 : Thermodynamics 6. 6. 1. Second Law of Thermodynamics 6. 8. Third Law of Thermodynamics Unit 7 : Equilibrium 7. 12. 1 pH of Buffer Solutions Class XII Unit 16 : Chemistry in Everyday Life 16. 4. 2. 1 Antioxidants 3 Unit 5: States of Matter 5. 7. 1 KINETIC ENERGY AND MOLECULAR SPEEDS As you have studied in the previous section the molecules of a gas are always in motion and are colliding with each other and with the walls of the container. Due to these collisions the speeds and the kinetic energies of the individual molecules keep on changing. However at a given temperature, the average kinetic energy of the gas molecules remains constant. If at a given temperature, n1 molecules have speed v1, n2 molecules have speed v2, n3 molecules have speed v3, and so on. Then, the total kinetic energy (EK) of the gas at this temperature is given by where m is the mass of the molecule. The corresponding average kinetic energy ( If the following term Then the average kinetic energy is given by where c is given by 4 ) of the gas will be This ‘c’ is known as root-mean-square speed. As the name implies, to calculate c, first take the squares of the individual speeds, then their mean and finally the square root of the mean. It can be shown that c is related to temperature by The average kinetic energy depends only on absolute temperature and is related to absolute temperature by the expression where k = Boltzmann constant = 1. 38 x 10-23 J K-1 In the case of gases, one also talks of two other speeds, namely, average speed and most-probable speed. The average speed ( ) at a given temperature is the arithmetic mean of the speeds of different molecules of the gas. . e, where n1 molecules have speed v1, n2 molecules have speed v2, n3 molecules have speed v3, and so on. The relationship between average speed and temperature T is given by The most probable speed ( ) of a gas at a given temperature is the speed possessed by the maximum number of molecules at that temperature. Unlike average speed and root mean sq uare speed, the most probable speed cannot be expressed in terms of the individual molecular speeds. The most probable speed ( ) is related to absolute temperature (T) by the expression 5 Relationship between different types of molecular speeds The three types of molecular speeds, namely, most probable speed ( ), average speed ( ) and root mean square speed (c) of a gas at a given temperature are related to each other as follows: For a particular gas, at a particular temperature, It follows from the above relationships that Example: Calculate the root mean square, average and most probable speeds of oxygen molecules at 27 oC. Solution: Given data: Molar mass of oxygen, M = 32 g mol-1 = 0. 032 kg mol-1 Temperature, t = 27 oC T = (27 + 273) K = 300 K 6 Expressions to be used: Root mean square speed, Average speed, Most probable speed, Actual calculations Root mean square speed, Average speed, Most probable speed, 5. 7. 2 MAXWELL-BOLTZMANN DISTRIBUTION OF MOLECULAR SPEEDS The speeds of the individual molecules of a gas do not remain constant. They keep on changing due to inter molecular collisions and due to collisions with the walls of the container. However, at a given temperature, the distribution of molecular speeds remains constant. This distribution of molecular speeds is given by Maxwell-Boltzmann distribution law. 7 For a given gas, at a given temperature, the distribution curve of molecular speeds is shown in Figure 5. 7. 1 Figure 5. 7. 1. Maxwell Boltzmann distribution curve You can see from the distribution curve that it is the plot of molecular speed vs the fraction of molecules. The important features of this distribution curve are: (i) The fraction of molecules having too low or too high speeds is very small. (ii) There is a certain speed for which the fraction of molecules is maximum. This speed is known as most probable speed. (iii) The most probable speed of a gas, is the speed possessed by the maximum number of molecules of the gas at a given temperature and it corresponds to the peak of the curve. Since the most probable speed ( xpression ) is related to absolute temperature T by the It means that at the same temperature, lighter gases shall move faster than heavier gases as is evident from the distribution curves of chlorine and nitrogen gases in Figure 5. 7. 2. 8 Figure 5. 7. 2. Maxwell Boltzmann distribution curves for chlorine and nitrogen gases at 300K Effect of temperature In Figure 5. 7. 3. are given t he Maxwell Boltzmann distribution curves of a gas at three different temperatures T1, T2 and T3 such that T1gt;T2gt;T3. Figure 5. 7. 3. Maxwell Boltzmann distribution curves for a gas at three different temperatures 9 It can be seen from these distribution curves that as the temperature increases 1. The entire curve shifts towards right. 2. The most probable speed increases. 3. The fraction of molecules having most probable speed decreases. 4. The curve becomes broader in the middle range indicating that more molecules have speeds near to the most probable speed. You read "Cbse Chemistry Notes for 11 and 12" in category "Papers" 5. The fraction of molecules having higher speeds increases. 6. The fraction of molecules having lower speed decreases. It may be noted that the total area under each of the curves remains the same as the sum of fractions of molecules remains unaltered on changing the temperature. 0 EXERCISE 1. Calculate (i) root mean square speed (ii) average speed and (iii) most probable speed of CO2 molecules at 700 K . 2. A sample of a gas contains 15 molecules with a speed of 3 m s-1, 25 molecules with a speed of 5 m s-1 and 30 molecules with a speed of 8 m s-1. Calculate root mean sq uare speed of these molecules. 3. Calculate the temperature at which the average speed of oxygen equals that of hydrogen at 20 K. 4. Calculate the temperatures at which the root mean square speed, average speed and the most probable speed of oxygen gas are all equal to 1500 m s-1. Answers 1. i. 629. 92, m s-1 ii. 80. 50 m s-1 iii. 514. 33 m s-1 2. 6. 187 m s-1 3. 320 K 4. T for root mean square speed= 2886 K, T for the average speed = 3399 K, T for most probable speed = 4330 K 11 12 Unit 6 : Thermodynamics 6. 6. 1 SECOND LAW OF THERMODYNAMICS You have already studied in the previous sections that the first law of thermodynamics deals only with the law of conservation of energy and it gives no information about the criteria for feasibility of a given physical or chemical process. This law is always obeyed whether a given process occurs on its own or is made to occur with the help of an external agency. In any case the first law is valid in both the forward and reverse direction of the process. You have also learnt about the concept of entropy which is a measure of the randomness or the disorder in a system. This concept helps in explaining the spontaneity of the irreversible processes. For an irreversible process, the entropy of the system and surroundings taken together i. e. of the universe increases, while for a process at equilibrium it remains constant. This conclusion is of great importance as it helps us to predict whether a given process can take place spontaneously or not. Since all processes in nature occur spontaneously i. e. irreversibly, it follows that the entropy of the universe is increasing continuously. This important statement i. e. â€Å"in any spontaneous process, the entropy of the universe (system and surroundings) always increases† is also known as the second law of thermodynamics. ?SUniverse = ? Ssystem + ? Ssurroundings Specifically it means that If ? SUniverse gt; 0, the reaction is spontaneous If ? SUniverse lt; 0, the reaction is non-spontaneous If ? SUniverse = 0, the reaction is at equilibrium Since chemists are generally more interested in the system (reaction mixture) than the surroundings, it is therefore more convenient to restate the second law in terms of the thermodynamic properties of the system, without regard to the surroundings. As already described in the previous section, this is possible through the Gibbs free energy G which for a system is defined as G = H – TS. In terms of this thermodynamic property, the second law of thermodynamics can be restated as in any spontaneous process at 13 constant temperature and pressure, the free energy of the system (? Gsystem) always decreases. According to this definition If ? Gsystem lt; 0, the reaction is spontaneous If ? Gsystem gt; 0, the reaction is non-spontaneous If ?Gsystem = 0, the reaction is at equilibrium 6. 8. THIRD LAW OF THERMODYNAMICS The third law of thermodynamics is concerned with determination of entropy. It states that a substance which is perfectly crystalline at absolute zero of temperature has an entropy of zero. In a perfect crystal at absolute zero of temperature, each constituent of the crystal (atom, molecule or ion) is at the proper crystal lattice site and it therefore has the lowest energy. This means that this particular state is of perfect order, i. e, has zero disorder and hence zero entropy. Using zero value of entropy at absolute zero for a perfectly crystalline substance as the reference point (initial state), one can calculate absolute value of entropy of the substance in any state (solid, liquid or gas) at any temperature by calculating ? S for the process/es in going from the initial state to the state of the substance for which entropy is to be calculated. However there are certain substances which possess certain entropy even at absolute zero. This entropy is known as residual entropy. The origin of residual entropy can be explained on the basis of the disorder which remains at absolute zero in certain crystals composed of AB types of molecules where A and B are similar atoms (as in CO). In such substances, there is a very little energy difference between â€Å"†¦AB AB AB†¦Ã¢â‚¬  and â€Å".. †¦AB BA BA AB†¦.. † and other arrangements so that the molecules adopt the orientations AB and BA at random in the solid. This gives rise to some disorder, also known as frozen disorder, and consequently residual entropy. For example in case of CO, the measured residual entropy is 5 J K-1 mol-1 which is close to the value expected for a random structure Figure 1 (B) of the form â€Å"†¦Ã¢â‚¬ ¦CO CO OC CO CO OC OC†¦Ã¢â‚¬ . 14 Figure 1. Alternative molecular arrangements for CO (A) Perfect crystal (B) Actual crystal EXERCISE 1. State Second Law of Thermodynamics. 2. Write the conditions in terms of ? H and ? S when a reaction would be always spontaneous. 3. When ? H gt; 0 and ? S lt; 0, a reaction is never spontaneous. Explain. 4. Comment on the spontaneity of a reaction at constant temperature and pressure in the following cases i) ? H lt; 0 and ? S gt; 0 (ii) ? H gt; 0 and ? S lt; 0 (iii) ? H lt; 0 and ? S lt; 0 (iv) ? H gt; 0 and ? S gt; 0 5. State third law of thermodynamics. 6. Explain the term residual entropy. 15 Unit 7: Equilibrium 7. 12. 1 pH OF BUFFER SOLUTIONS : HENDERSON – HASSELBALCH EQUATION As you have already learnt in the previous section a buffer solution is a soluti on which resists change in its pH on the addition of small amount of acid or a base. Most of the important buffer solutions generally consist of mixtures of weak acids and their salts or weak bases and their salts. These buffer solutions are known as acidic buffers and basic buffers respectively. If the pH of the buffer solution is less than 7, it is called an acidic buffer and if the pH of the buffer solution is greater than 7 it is called a basic buffer. Examples of some acidic and basic buffers are as given below Acidic buffer Basic buffer 1) Acetic acid and sodium acetate 1) Ammonium hydroxide and ammonium chloride 2) Formic acid and sodium formate 2) Ammonium hydroxide and ammonium nitrate pH of an acidic buffer A very common example of an acidic buffer is a mixture of acetic acid and sodium acetate. Acetic acid, being a weak acid, is very slightly dissociated, while sodium acetate being a salt is completely dissociated. The mixture thus contains acetic acid molecules as well acetate ions and sodium ions. At equilibrium: CH3COOH(aq) H+ (aq) + CH3COO-(aq) Taking the negative logarithm on both the sides, we get 16 †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦(7. 39) In general, †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦(7. 40) It may be noted that the concentration of the acetate ions is taken to be almost equal to the concentration of the salt because the acetate ions coming from fully dissociated salt (here sodium acetate) suppress the ionization of the weak acid (acetic acid). This equation (7. 0) is called Henderson- Hasselbalch equation. According to this equation, the pH of an acidic buffer consisting of a mixture of a weak acid and its salt depends on the pKa of the acid, and the concentrations of the salt and acid in the mixture. If concentration of the sa lt is equal to that of the acid, then Buffer action of Acidic buffer The buffer action of an acidic buffer consisting of a mixture of acetic acid and sodium acetate can be explained in the following way. If we add small amount of HCl to the buffer solution it will ionise to give H+ ions. These combine with CH3COO- ions to form weakly ionized acetic acid. CH3COO-(aq) + H+(aq) ? CH3COOH(aq) + H2O(l) Since H+ ions get neutralised by CH3COO- ions, there will be no change in pH. On the other hand, if we add a few drops of NaOH to the buffer solution, it provides OH- ions which are neutralized by the acetic acid present in the mixture. 17 OH-(aq) + CH3COOH(aq) ? CH3COO-(aq) + H2O(l) Therefore the pH of the solution remains unchanged. pH of a Basic Buffer A very common example of a basic buffer is a mixture of ammonium hydroxide and ammonium chloride. Ammonium hydroxide being a weak base is very slightly dissociated, while ammonium chloride being a salt is completely dissociated. The mixture thus contains ammonium hydroxide molecules as well as ammonium ions and chloride ions. At equilibrium, NH4OH(aq) NH4+(aq) + OH-(aq) Taking the negative logarithm on both the sides, we get †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦(7. 41) In general, †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦(7. 42) 18 It may be noted that the concentration of the ammonium ions is taken to be almost equal to the concentration of the salt because ammonium ions coming from the fully dissociated salt (here ammonium chloride) suppress the ionization of the weak base ammonium hydroxide. This equation (7. 42) is called Henderson- Hasselblach equation. Further, pH can be calculated easily from pOH using Hence, It may be noted that pKa + pKb = 14 Buffer action of basic buffer The buffer action of a basic buffer consisting of a mixture of ammonium hydroxide and ammonium chloride can be explained in the following way. If a few drops of HCl are added to the buffer solution, it will ionise to give H+ ion which will combine with OH- ions to form H2O. H+(aq) + OH- (aq) ? H2O(l) Therefore, the addition of HCl will not change the pH. On the other hand, when a few drops of NaOH solution are added to the buffer solution, it would give OH- ions. These OH- ions combine with NH4+ ions present in the solution to form NH4OH, which is only slightly ionised. OH-(aq) + NH4+ (aq) ? NH4OH(aq) Hence, the addition of a base also will not change the pH. 19 EXERCISE 1. A certain buffer is made by mixing sodium formate and formic acid in water. With the help of equations explain how this buffer neutralizes addition of a small amount of an acid or a base. 2. A basic buffer is made by mixing ammonium hydroxide and ammonium nitrate in water. Explain how this buffer resists change in its pH on addition of a small amount of an acid or a base. 3. What would be the pH of a solution obtained by mixing 10 g of acetic acid and 15 g of sodium acetate and making the volume equal to 1 L. Dissociation constant of acetic acid at 25oC is 1. 75 x 10-5. 4. A buffer solution contains 0. 40 mol of ammonium hydroxide and 0. 50 mol of ammonium chloride to make a buffer solution of 1 L. Calculate the pH of the resulting buffer solution. Dissociation constant of ammonium hydroxide at 25oC is 1. 81 x 10-5. Answers 3. pH = 4. 80 4. 9. 161 20 Class XII Unit 16: Chemistry in Everyday Life 16. 4. 2. 1. ANTIOXIDANTS Antioxidants are one of the important and necessary food additives. These compounds retard the action of oxygen on food thus reducing its speed of decomposition by oxidation. Hence they help in the preservation of food. These act as sacrificial materials, i. e. these are more reactive towards oxygen than are the materials they are protecting. They also reduce the rate of involvement of free radicals in the aging process. Examples: The two most familiar antioxidants used are butylated hydroxy toluene (BHT) and butylated hydroxy anisole (BHA) (Figure 1). These phenolic compounds are added to preserve fats in packaged food. Oxygen reacts preferentially with BHA or BHT rather than oxidizing fats or oils, thereby protecting them from spoilage. The addition of BHA to butter increases its storage life from months to years. Sometimes, BHT and BHA are added in combination with citric or ascorbic acids to produce a more active synergetic effect. Figure 1: Butylated hydroxy toluene (BHT) and butylated hydroxy anisole (BHA) Sulphur dioxide and sulphites ( such as sodium sulphite, sodium bisulphite and sodium metabisulphite) are useful antioxidants for wine and beers, sugars syrups and cut, peeled or dried fruits and vegetables. They prevent or reduce their discoloration. 21 EXERCISE 1. Name one antioxidant commonly used to increase the storage life of butter. 2. Name one antioxidant used in wine and beers. 22a How to cite Cbse Chemistry Notes for 11 and 12, Papers

The Girl in the Studio free essay sample

The rush of nerves overwhelms my body when I follow my team to the curtain. I hear the crowd roaring waiting for our appearance. This rush of excitement and fear almost devoured me until they announced our team. Pushing back the curtain, we run out onto the mat and wave to the crowd with fake smiles holding back our nervous mindset. I move to my spot and clench my fists while whispering â€Å"Let’s do this† just loud enough for my team to hear it. Once the music begins I lose all sense of fear and tenseness. It almost feels like I’m watching myself perform with my team from the crowd. I lose myself in the music and perform as if I wasn’t nervous at all. The 3 minutes we performed only felt like 5 seconds. Immediately when we are done performing I hear the crowd scream in joy and I hear cheering from our other teams. We will write a custom essay sample on The Girl in the Studio or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page We all run off the mat, hug each other and remind ourselves that this is why we dance. Dancing is defined as â€Å"to move ones feet or body, or both, rhythmically in a pattern of steps, especially to the accompaniment of music† but, dancing is so much more than that. Dance for me is a release, a place for me to be myself and release any feelings I have in a positive way. When I went to my other school I was bullied a lot because I was from the city and I was â€Å"different†. They tended to pick on my clothes and how I talked. I felt like I couldn’t escape my life and no matter how much I talked about it to an adult the torture never stopped. At one point even teachers went along with the bullying. Every day I cried and begged my mom to let me stay home from school and my grades plummeted tremendously. I felt like I was at the weakest, lowest point of my life. Before I exploded from everything Ive been bottling up, I joined dance. I think dance saved my life. I used my feelings to become a great competitive dancer. I spend many hours in the dance studio just practicing and even letting off some steam. I dance with my soul, you can see who I am by watching me dance. Its easy to show dramatically immense emotion in dance especially in Hip Hop (which is the type of dance I do). I think putting everything you can into a dance can make it magical. It can almost make it look like a movie and the dancer is the actor. You dont need any words to figure out whats going on, the voice is in the dance. I think my dancing has improved dramatically since I moved to a new school. Im happier and have many learned lessons under my belt. My mom told me that you can actually see that Im happier even in my routines. I learned to be myself and maybe there isnt such a thing as being normal. I enjoy my quirky weirdness and continue to embrace it. Now that I have a higher self esteem, I continue to thrive in dance because Im no longer afraid of judgment. Dancing has shaped my life and Ill continue to be that girl in the studio.

Business Meeting Etiquettes in Japan

Question: Describe about the Business Meeting Etiquettes in Japan? Answer: The Japanese business meetings etiquettes form the most quint essential base to nail a business deal in Japan. There are various greeting rituals and types of non-verbal communications considered as very essential gestures. Japanese are very sensitive towards these gestures. The basic gestures that must be followed in the meeting of Sandwich blitz are taking prior appointments much before the meeting. Once the meeting is fixed, the delegates should present their business cards with two hands. The business card written on both the sides is mostly preferred, written in both English and Japanese. The business attire should be taken care of (Japanventure.com, 2015). The men should be dressed in dark shades. Personal habits are also very noticeable in Japanese meetings. The non-verbal communication may include the bowing (Kwintessential.co.uk, 2015). It is mandatory to greet one another by bowing amongst the Japanese, however they are slight liberal when it comes to foreigners but it`s be tter to bend a slight. Things to know prior the meeting: Dalman and Lei should know all the information regarding Sandwich Blitz and Lei as lack of adequate information may led to inconvenience. All the papers should be ready prior the meeting, as delay is considered as a negative attitude. Apart from non-verbal communication and other gestures, the body language of the client is to be very appropriate. Hence, the business decisions are influenced a lot by the gestures of the clients during Japanese meetings (Hussain, 2010). References Hussain, S. (2010).Business etiquettes. Jaipur: Yking Books. Japanventure.com,. (2015). Retrieved 5 February 2015, from https://www.japanventure.com Kwintessential.co.uk,. (2015).Japan - Language, Culture, Customs and Etiquette | global-etiquette | resources. Retrieved 5 February 2015, from https://www.kwintessential.co.uk/resources/global-etiquette/japan-country-profiles.html

Why should people allow marrying only after age 30

Why should people allow marrying only after age 30 Introduction One of the mainly sure ways to progress the physical condition and well-being of the world’s inhabitants is to hearten and shore up the thought of marriage.Advertising We will write a custom essay sample on Why should people allow marrying only after age 30? specifically for you for only $16.05 $11/page Learn More The continued researches divulges that, the married people are normally bodily healthier, more contented, survives longer, enjoys enhanced mental health, are more satisfied and less expected to suffer corporeal abuse. Premarital cohabitation does not convey the equal advantage nuptials do. As a substitute, it conveys amplified variance and hostility as well as amplified probability of break up in later marriages. Dr. Robert H. Coombs, one of the researchers, showed that, â€Å"married people live longer and generally are more emotionally and physically healthy than the unmarried. If this is the case, why should there be a fixed age of marriage and yet marriage brings total happiness, good healthy, mental health and extended life span in human being? According to Dr. Robert H. Coombs research, he totally disagrees that people should be allowed to marry only after the age of 30. To start with, he quotes a verse in the bible that says, â€Å"It’s better to marry than to burn up†. According to the verse, he noted that, this verse was not there for the people over thirty years but for the people who could not resist sexual behaviors. Nowadays, the high rates of sexual transmitted diseases are highly spread by the youths who are have not attained the age of thirty and not married. If age is put aside, and every one who cannot withdraw his/her sexual temperature by the help of the people is allowed to marry, this would reduce the rate of sexual transmitted diseases. Another reason as to why I disagree on marriage after the age of 30 is that, many psychological related problems are experienced by th e people who are not married. If any one who feels ready to marry regardless the age is given the access, then the rate of deaths relating to psychological problems will be reduced. Dr. Robert H. Coombs, in his research, commended that, if age was not the key factor to marriage, then the high rate of deaths caused by; alcoholism, suicides, loneliness, Psychiatric problems, and Morbidity and mortality would be highly reduced. He also said, if anybody who felt like marrying regardless the age was genuinely given the opportunity and backed by the other members, then this would lead to happiness hence kicking out the high chances of psychological related problems.Advertising Looking for essay on social sciences? Let's see if we can help you! Get your first paper with 15% OFF Learn More Finally, the reason as to why I disagree on marriage after the age of 30 is that, it brings about use of drugs. As a result of the latest science and technology, people are getting a lot of money while still young and not married thus indulging to some drug behaviors like the use of cocaine’s, alcohol among others. If the freedom of marriage regardless the age is unrestricted and people marrying, the time of using all these drugs will not be got because of the many responsibilities of a family thus bringing about raising a good generation without contractions. Conclusion One of the mainly sure ways to progress the physical condition and well-being of the world’s inhabitants is to hearten and shore up the thought of marriage. Marriage brings about happiness, enhanced mental health, and long life span among others. If this is the case, I disagree with the statement that says that, people should be allowed to marry only after the age of 30. The essay puts across that, marrying after 30 years; there would be likely cases like psychological related problems, use of drugs and high sexual behaviors. Giving access to every one who feels like marrying an d supported by the other people would lead to the global expansion.

Thylacoleo (Marsupial Lion) - Facts and Figures

Thylacoleo (Marsupial Lion) - Facts and Figures Name: Thylacoleo (Greek for marsupial lion); pronounced THIGH-lah-co-LEE-oh Habitat: Plains of Australia Historical Epoch: Pleistocene-Modern (2 million-40,000 years ago) Size and Weight: About five feet long and 200 pounds Diet: Meat Distinguishing Characteristics: Leopard-like body; powerful jaws with sharp teeth About Thylacoleo (the Marsupial Lion) Its a commonly held misconception that that the giant wombats, kangaroos and koala bears of Pleistocene Australia were only able to prosper thanks to the lack of any natural predators. However, a quick glance at Thylacoleo (also known as the Marsupial Lion) puts the lie to this myth; this nimble, large-fanged, heavily built carnivore was every bit as dangerous as a modern lion or leopard, and pound-for-pound it possessed the most powerful bite of any animal in its weigh classwhether bird, dinosaur, crocodile or mammal. (By the way, Thylacoleo occupied a different evolutionary branch from saber-toothed cats, exemplified by the North American Smilodon.) See a slideshow of 10 Recently Extinct Lions and Tigers As the largest mammalian predator in an Australian landscape teeming with oversized, plant-eating marsupials, the 200-pound Marsupial Lion must have lived high on the hog (if youll forgive the mixed metaphor). Some paleontologists believe that Thylacoleos unique anatomyincluding its long, retractable claws, semi-opposable thumbs and heavily muscled forelimbsenabled it to pounce on its victims, quickly disembowel them, and then drag their bloody carcasses high up into the branches of trees, where it could feast at its leisure unmolested by smaller, peskier scavengers. One odd feature of Thylacoleo, albeit one that makes perfect sense given its Australian habitat, was its unusually powerful tail, as evidenced by the shape and arrangement of its caudal vertebrae (and, presumably, the muscles attached to them). The ancestral kangaroos that coexisted with the Marsupial Lion also possessed strong tails, which they could use to balance themselves on their hind feet while warding off predatorsso its not inconceivable that Thylacoleo could tussle for short periods on its two hind feet, like an oversized tabby cat, especially if a tasty dinner was at stake. As intimidating as it was, Thylacoleo may not have been the apex predator of Pleistocene Australiasome paleontologists claim that honor belongs to Megalania, the Giant Monitor Lizard, or even the plus-sized crocodile Quinkana, both of which may have occasionally hunted (or been hunted by) the Marsupial Lion. In any case, Thylacoleo exited the history books about 40,000 years ago, when the earliest human settlers of Australia hunted its gentle, unsuspecting, herbivorous prey to extinction, and even sometimes targeted this powerful predator directly when they were especially hungry or aggravated (a scenario attested to by recently discovered cave paintings).

Wireless Networking (WLAN) Essay Example | Topics and Well Written Essays - 2000 words

Wireless Networking (WLAN) - Essay Example Using these devices users can access shared information conveniently without having to plug in and connect to other devices physically. The transmission of data between devices in the network takes place by the simple process of modulation with radio frequencies acting as carriers of the information being transmitted. The RF is modulated according to the information signal and carried to the receiving end. At the receiving end the exact information is extracted from the modulated signal by the process of demodulation. A number of signals can be transmitted through air at the same time provided that their frequencies have a considerable gap between them. In other words the frequency of operation should be different and they will not interfere. There are one or more devices known as ‘access points’ through which the wireless devices communicate. An access point (AP) is a simple transmitter/receiver or ‘Transceiver’. A wireless network interface card (NIC) is required to access a wireless network which is available in various forms. Nowadays devices are available with built in NIC’s. But they can also be installed separately latter. These NIC’s also require necessary software drivers to be installed for their functioning. Narrowband WLAN’s keep the bandwidth of the radio frequency signal as narrower as possible, in order to just pass the information. Although the distance between the devices is reasonable but the speeds achieved are not as good as required by the corporate users. A general problem that could arise in WLAN’s is the interference, which can be overcome by allotting different frequencies to different individuals. In this case since the bandwidth is narrow, interference can very well be avoided. These WLAN’s use wideband RF. The use of wideband signal helps in attaining greater speeds. The most popular WLAN being used is 802.11b attaining a speed of about 11 Mbps. With the advancement of technology the speeds

The Death of Marilyn Munroe Research Paper Example | Topics and Well Written Essays - 1000 words

The Death of Marilyn Munroe - Research Paper Example The police officer drove to her home and confirmed that she was indeed dead. However, there were many questions about Marilyn’s death, which needed answers, moreover, till to date there are questions that beg to be answered. Different explanations and theories that have been forwarded to explain her death especially accidental, suicide or murder, which can be explored to determine which is the most credible and why despite the fact that an official report on her death was issued (Possible suicide) the story is still subject to a myriad of speculations. Despite the plethora of theories, the official explanation is still the most logical, and despite the many loose ends and mysterious circumstances surrounding it, it best explains the available facts. However, one must take cognizance of the fact that, like the others, it was not a watertight explanation. The most sensational and explored theory was that she was murdered. This is highly characteristic in celebrity deaths, and of ten a cottage industry of conspiracy theories spouts in the wake of one. The reason the murder conspiracy theory generated so much interest was the implicating the two most powerful men in America, President J.F Kennedy and his brother Robert Kennedy. It is alleged from several unverifiable sources that Monroe was having an affair with the president whose amorous nature was â€Å"a well-known secret†. However, due to her irrational behavior and that fact that she had become somewhat obsessed with the idea of becoming first lady, Kennedy decided to cut her loose. Several witnesses, one of them a police officer alleged to have seen Robert near the scene on the death. Is it possible that one or both of them could have been complicit in the death of the actress? It was claimed that security agents might have killed her in order to cover up for the brothers indiscretions, since they are said to have discussed national security issues with her. That question may appear easy to a co nspiracy theorist trying to make the most sensational story, but the lack of evidence and the moral standing of the attorney general make it a decidedly unlikely story. However, there is evidence of a cover up in that there was a lot of missing evidence or evidence that seemed to have been tampered with. The autopsy results also left many questions since and many factors did not add up. Telephone records of the night were confiscated, and despite the official assumption that she swallowed the pills, there was no evidence of water or a glass in her room. There were also allegations that the body had been posed to appear like suicide, however, tampering with evidence is an entirely different thing from murder so one cannot presume that she was killed. The theory of accidental death is more credible than the murder, possibly owing to the fact that there was empirical evidence supporting it. However, due to its non-sensational nature, it has not been as explored as the former. On the pr emises that the death was accidental, there two distinct possibilities, one is that she overdosed herself by accident, or she was taking wrongly prescribed medication. Drs. Greenson and Hymans had been working together to wean her of Nembutal the drug which she is believed to have been one of those responsible for the death. Another consideration was that the doctor, who gave Monroe a heavy dose of Chlorate on the eve of her death, might not have done so if he knew she