Junior Inter Chemistry Questions and Answers
1. What is disproportionation reaction? give one example.
Ans: The redox reaction in which same species undergo oxidation as well as reduction
e.g: 2 H2O2 → 2 H2O + O2
2. Give the biological importance of magnesium and calcium ions.
Ans: Magnesium containing chlorophyll in plants absorb light. Enzymes containing magnesium take part in ATP reactions to release energy.
Calcium is present in bones and teeth. Calcium is essential for blood coagulation.
3. Why gypsum is added to cement?
Ans: 3% gypsum is added to cement inorder to slowdown the process of setting of the cement.
4. What is allotropy? Name two crystalline allotropes of carbon?
Ans: Existence of an element in many physical forms but possessing similar chemical properties is called allotropy.
e.g: Diamond, Graphite.
5. What is Gibbs energy?
Ans: The difference in the enthalpy (H) and the product of entropy (S) and absolute
temperature (T) of the system.
G = H − TS
6. Write any four important postulates of kinetic molecular theory of gases.
Ans: At ordinary temperature and pressure, there is no force of attraction between the
★ Molecules of a gas are in constant and random motion.
★ Collisions of gas molecules are perfectely elastic.
★ Average kinetic energy of gas molecules ∝ T
7. What are the harmful effects of acid rains?
Ans: ★ Acid rain damages buildings and historical monuments.
★ Acid rain affects plants, aquatic animals.
8. What is green house effect? and how is it caused?
Ans: Heating of the earth’s surface (atmosphere) is called green house effect. It is caused due to absorption of infra red radiation by the gases such as CO2, CH4, O3, water vapour and C.F.C.s
a) Graphite functions as a lubricant
b) Graphite is a good conductor of electricity
a) As the Layers in graphite are held together by weak Vander waal’s forces of attraction, graphite layers can slip one over the other, so it acts as lubricant.
b) The fourth valence electron of carbon remains unpaired and these electrons makes graphite a good conductor of electricity.
10. (a) What is buffer solution?
(b) Aqueous Solution of NH4Cl is acidic, where as that of CH3COONa is basic. Why?
(a) The solution which can resist the change in pH on addition of few ml of acid or base is called buffer solution.
(b) Due to cationic hydrolysis, aqueous solution of NH4Cl is acidic. Due to anionic hydrolysis, aqueous solution of CH3COONa is basic.