Chaper-4. CARBON AND ITS COMPOUNDS
Q-1. Mrs. Anita observed that her cooking utensils are becoming black in colour and the flame of her gas stove is yellowish in colour what can be the reason for this sooty flame. How is this problem harmful for our environment? What steps should be taken to stop this process.
Ans: a).The inlets for air in stove get blocked which leads to yellow flame.
b). This problem is harmful for our environment as incomplete combustion results in the formation of oxides which are major pollutants of our environment.
c). For preventing this situation gas or stove burners should be cleaned time to time.
Associated Value : Eco-friendly habits will be inculcated among the learners
Q-2. Ethanol is used on a large scale at commercial level this is a very useful chemical. It is commonly called alcohol and is the active ingredient of alcoholic drink. But consumption of alcohol also causes drunkenness and this practice is Socially condemned. As a responsible student of class –X what steps you would take to discourage the use of alcohol.
Ans: By sensitizing the people about the harmful effects of liquor consumption.
By making poster, banners and writing articles on this issue.
By not getting attracted towards this habit and to stop my friends also to keep control on themselves to condemn alchololism.
Associated Value : The learners understand the bad effects of Alcoholism and also start try to discourage this practice in the society.
Q-3. You must have seen advertisements stating that some vegetable oils are healthy. Saturated fatty acids which are said to be harmful for health. Why vegetable oils are considered healthy then aturated fatty acids (ghee)? What precautions you would take in selecting a cooking oil.
Ans: Vegetable oils contain unsaturated fatty acids which are healthy and decrease the cholesterol level in our blood. That is why we should use vegetable oils for cooking. Cooking oil should be selected in such a manner that it should contain low cholesterol.
Associated Value : The learners will be able to adopt healthy food habits once they understand that animal fats produce more cholesterol than vegetable oil.
9th Chapter- work and Energy-Activity based Question Solutions
1. Is work done when you are reading book?
Ans: No ,it is because there is no displacement in body.
2. Are you doing work when you are pushing wall or huge rock?
Ans: No work is done as rock does not move. Energy using this time is converted as heat energy in body.
3. Give an application where a body displaces without application of work?
Ans: Object displaced itself on inclined plane without application of work.
4. Idenfy two situation where object does not show displacement by the application of work?
Ans: The two situations are:
(i) if you push a mighty object
(ii) If balanced force act on a body
5. Name an energy cause by sun?
6. Name the two source of energy which are not due to sun?
Ans: Nuclear energy and Geo thermal Energy
7. What happen if you are doing work without changing velocity of object?
Ans: You work is stored in the form of potential energy. For example: When you compress slinky work done get stored in the form of Elastic potential energy.
8. Write the expression for power for a body having constants speed?
Ans: P = Work /velocity
9. How can you say that sun is cause of hydro electricity?
Ans: Solar energy evaporates water and help to form clouds. Cloud get down on the earth as rain. This water runs in river that is store in dam at high altitude. When this water allow falling rotate turbine and generating electricity. Thus that sun is cause of hydro electricity.
10. How is the dropping of ball from height is the an example of conservation of energy?
Ans: When ball is dropped from high its gravitational potential energy decrease and at same time kinetic energy increases as it gain speed.
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Class - X Chapter: Carbon and Its Compounds
1.Q. What happen when few drops of alkaline KmNO4 added to Ethanol?
Ans: In the begging color of KmNO4 disappear. When excess KmNO4 is dissolved in solution colour cannot disappear because whole Ethanol gets oxidized into Ethanoic acid.
CH3CH2OH ----- KmNO4------Heat------->CH3COOH
Hence, alkaline KmNO4or Acidified K2Cr2O7 oxidized alcohol into ethanoic acid
2.Q. How can we convert unsaturated hydrocarbon into saturated hydrocarbon?
Ans: By the addition reaction of unsaturated hydrocarbon with halo atom in the presence of catalyst.
HC=CH +H2 -------------Ni--------5700 K------> Ch3-CH3
R2C=CR2 + H2 ------------Ni---------> R2HC-CHR2 (Vegetable Gee)
This reaction is known as Hydrogenation reaction.
3. Q. How can you test that given hydrocarbon is unsaturated?
Ans: When few drops of Bromine is added to unsaturated hydrocarbon its colour disappear due to addition reaction.
For example: If drops of bromine water added to ethyne, the colour of Bromine disappear due to addition reaction. HC≡CH + Br2 -------------> HBr2 C – CHBr2 (Tetra room ethane is formed)
4. Q. How can you prepare alkenes from Ethanol?
Ans: When Ethanol heated in presence of Conc.H2SO4 or Al2O3 at 6230C ,Ethanol loose water molecules and form alkenes. C2H5OH ---H2SO4------6230C------>CH2=CH2 + H2O
5. Q. What happen when a piece of sodium metal added to Ethanol?
Ans: Sodium ethoxide is formed with evolution of H2 gas
C2H5OH + Na -------------> C2H5ONa + H2
6. Q. What happens when few drops of Conc.H2SO4 is added to Solution of Ethanoic acid and Ethanol?
Ans: A substance with fruity smell is formed called Ester.This reaction is known as Esterification
C2H5OH + CH3COOH ------H2SO4------> CH3COO C2H5 (Ester or, Ethyl Ethanoate)
7. Q. What types of flame produce by burning of Benzene, Nepthline and Camphor?
Ans: Smoky flame due presence of excess carbon content.
8. Q. What is Gasol?
Ans: The mixture of petrol with alcohol up to 20% is known gasol.
9.Q. Why Acetic acid is called glacier acid?
Ans: Acetic acid freezes at 290K in cold weather and form crystals.This is why acetic acid is called glacier acid.
10.Q. What is saponification?
Ans: When sodium hydroxide react with ester and form alcohol and sodium Ethanoate. This reaction is used to form soap So this reaction is known as saponification.
CH3COO C2H5 + NaOH ------------> CH3COONa + C2H5OH
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Solved Questions:CBSE :Chemistry: Chapter-Periodic Classifications
1. Define valency and describe its variation in a period and a group.
Ans: Valency of an element is its combining capacity.
Valency of an element = number of valence electrons (if equal to or less than 4)
Valency of an element = 8 â number of valence electrons (if more than 4)
2. What happens to the metallic character of the elements as we move in a period from left to right in the periodic table? Give reason.
Ans: Metallic character of the element decreases along a period due to decrease in atomic size along a period or outermost electrons are closer to nucleus. So they cannot be easily lost.
3. How were the positions of different isotopes decided in modern periodic table?
Ans: All the isotopes of an element have same atomic numbers. In modern periodic table, the elements have been allotted places based on their atomic numbers. Therefore, all the isotopes of an element have been assigned the same position in the modern periodic table
4. Where do you think hydrogen should be placed in the modern periodic table?
Ans: The modern periodic table is based on the atomic numbers of the elements and also upon their electronic distribution. Alkali metals as well as hydrogen have one electron in their valence shell. Therefore, hydrogen should be placed in the group of alkali metals. However, it has been assigned a separate position and is not a member of the group of alkali metals since it is a non-metal.
5. How were the positions of the elements Co and Ni resolved in the modern periodic table?
Ans: On the basis of atomic masses, Ni (58.7) should be placed before Co (58.9). This was defect in Mendeleevâs table because the element Co was placed before Ni. However, the atomic number of (Co = 27) is less than that of Ni ( 28). Therefore, they have been correctly arranged in the modern periodic table.
6. The two isotopes of chlorine have atomic masses 35 u and 37 u. Should they be placed in same slot in the periodic table?
Ans: Yes, they should be placed in the same slot because periodic table is based on the atomic numbers of the element and both the isotopes of chlorine have the same atomic number (Z = 17).
7. Which element is bigger in size, lithium (Z = 3) or Sodium (Z = 11) and why?
Ans: Lithium (Li) atom has only two shells K and L in it whereas a sodium (Na) atom has three shells K L and M. Since a sodium atom has one mote shell than a lithium atom, therefore sodium atom is bigger in size.
8. What were the criteria used by Mendeleev in creating his periodic table?
Ans: Ans. Mendeleevâs periodic table was based on the observation that properties of the elements are a periodic function of their atomic masses. This means that if elements are arranged in the increasing order of their atomic masses, then elements with similar properties get their place in the same group in a successive increasing order of atomic masses.
9. Why did Mendeleev leave some gaps in his periodic table?
Ans. Mendeleev left gaps in his periodic table to keep the elements with similar properties together. I-fe predicted dat new elements would be discovered later and they would occupy those gaps.
10. Why did Mendeleev treated the hydrides and oxides of element as the basic properties of elements for their classification?
Ans. During the period when Mendeleev gave his periodic table atomic numbers and electronic configurations were not known. Comparison of properties of elements could be best done by comparing their compounds. He selected oxides and hydrides because oxygen and hydrogen form compounds with most of the elements due to their high reactivity.
11. Why are the elements in the same group of the periodic table show close resemblance in their chemical behavior?
Ans: The chemical properties depend upon the number of valence electrons of an element. The elements in the same group of the periodic table show close resemblance in their chemical behavior as they have same number of valence electrons.
12. What happens to atomic radii in a group and period and why?
Atomic radius is the distance between the centre of atom and the outermost shell.
In a period, atomic radius generally decreases from left to right.
In a period there is a gradual increase in the nuclear charge. Since valence electrons are added in the same shell, they are more and more strongly attracted towards nucleus. This gradually decreases atomic radii.
Atomic radii increase in a group from top to bottom.
As we go down a group the number of shells increases and valence electrons are present in higher shell and the distance of valence electrons from nucleus increases. Also, the number of filled shells between valence electrons and nucleus increases Both the factors decrease the force of attraction between nucleus and valence electron. Therefore, atomic size increases on moving down a group.
13. Why are the ionization energy of elements increases in a period from left to right.
Ans: The minimum amount of energy required to remove an electron from a gaseous atom in its ground state to form a gaseous ion is called ionization energy.
The ionization energy increases in a period from left to right. This is because the force of attraction between valence electron and nucleus increases in a period from left to right.
14. What do you mean by is vary in group and periods in modern periodic table?
Ans: The tendency of element to gain an additional electron. This ability is measured by electron affinity. It is the energy change when an electron is accepted by an atom in the gaseous state. Electron affinity is assigned a positive value when energy is released during the process. Greater the value of electron affinity, more energy is released during the process and greater is the tendency of the atom to gain electron.
In a group, the electron affinity decreases on moving from top to bottom as less and less amount of energy is released.
In a period, the electron affinity increases from left to right, as more and more amount of energy is released
15. What do you mean by
Periodic Properties of Elements in modern periodic tables Class X (10th)
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Check your understanding:
1) What is the atomic radius of an atom?
2) What is the trend in atomic radius across a period?
3) The trend in atomic radius across a period is caused by _____.
4) What generally happens to atomic radii as one goes down a group or a family?
5) Write the equation for the ionization of an atom.
6) What is an ion?
7) What is ionization energy?
8) Which group or family has the lowest ionization energy?
9) Group 18 or 8A, the noble gases, have the highest ionization energy (True or False).
10) Elements with a high ionization energy lose electrons easily (True or False).
11) The increase in ionization energy across a period is caused by _____.
12) Why does ionization energy generally decrease going down a group or family?
13) What is meant by electron shielding?
14) What is the second ionization energy of an atom?
15) What is electron affinity?
16) Write the equation for electron affinity for an exothermic process.
17) Write the equation for electron affinity for an endothermic process.
18) Which group or family gains electrons most easily?
19) What is a cat ion?
20) What is an anion?
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