Q.1. Match the important chemicals given in Column (A) with the chemical formula given in Column (B).
Q.2. What will be the action of the following substances on litmus paper?
Dry HCl gas, Moistened NH3 gas, Lemon juice, Carbonated soft drink, Curd, Soap solution.
Q.3. Name the acid present in ant sting and give its chemical formula. Also, give the common method to get relief from the discomfort caused by the ant sting.
Ans. Ant sting contains methanoic acid (formic acid). Its chemical formula is HCOOH. The common method to get relief is to apply a paste of NaHCO3 (baking soda) on it or any basic substance to neutralize it.
Q.4. What happens when nitric acid is added to eggshell?
Ans. Egg-shell is made up of calcium carbonate, which will react with HNO3 to form CO2 (g) and H2O (l) along with calcium nitrate.
Example: CaCO3 + 2HNO3 → Ca(NO3)2 + CO2 + H2O
Q.5. A student prepared solutions of (i) an acid and (ii) a base in two separate beakers. She forgot to label the solutions, and litmus paper is not available in the laboratory. Since both the solutions are colourless, how will she distinguish between the two?
Q.6. How would you distinguish between baking powder and washing soda by heating?
Q.7. Salt A, commonly used in bakery products on heating, gets converted into another salt B, which itself is used for removal of hardness of water, and a gas C is evolved. The gas C, when passed through lime water, turns it milky. Identify A, B, and C.
Q.8. In one of the industrial processes used for the manufacture of sodium hydroxide, a gas X is formed as a by-product. The gas X reacts with lime water to give a compound Y, which is used as a bleaching agent in the chemical industry. Identify X and Y giving the chemical equation of the reactions involved.
Ans. Sodium chloride is used for manufacture of sodium hydroxide, which is called chloralkali process. In this process, chlorine and hydrogen gas are formed as byproducts along with sodium hydroxide. Chlorine gas gives bleaching power when reacts with lime water and used as a bleaching agent in chemical industries.
► 2NaCl(aq)+2H2O(l) → 2NaOH(aq)+Cl2(g)+H2(g)
► X→Cl2 (Chlorine gas)
► Ca(OH)2+Cl2 ⟶ CaOCl2+H2O
The gas X is chlorine.
Compound Y is calcium oxychloride which is commonly known as bleaching powder and used as a bleaching agent in chemical industries.
Q.9. Fill in the missing data in the following table
Q.10. What are strong and weak acids? In the following list of acids, separate strong acids from weak acids.
Hydrochloric acid, citric acid, acetic acid, nitric acid, formic acid, sulphuric acid.
Q.11. When zinc metal is heated with a dilute solution of a strong acid, a gas is evolved hydrogenation oil. Name the gas evolved. Write the chemical equation of the reaction involved and also write a test to detect the gas formed.
Ans. When zinc metal is treated with a dilute solution of a strong acid, hydrogen gas is evolved.
► Zn + 2HCl → ZnCl2 + H2
If we bring a burning splinter near the mouth of the test tube, the gas burns with a pop sound.
Q.12. In the following schematic diagram for the preparation of hydrogen gas as shown in the given figure, what would happen if the following changes are made?
(a) In place of zinc granules, the same amount of zinc dust is taken in the test tube.
(b) Instead of dilute sulphuric acid, dilute hydrochloric acid is taken.
(c) In place of zinc, copper turnings are taken.
(d) Sodium hydroxide is taken in place of dilute sulphuric acid, and the tube is heated.
(a) The reaction will become faster because zinc dust has more surface area.
(b) Nearly the same amount of hydrogen gas will be evolved.
(c) No reaction will take place as copper is less reactive than hydrogen.
(d) The reaction will take place, and hydrogen gas will be evolved.
Q.13. A metal carbonate X on reacting with an acid gives a gas which, when passed through a solution Y, gives the carbonate back. On the other hand, a gas G that is obtained at anode during electrolysis of brine is passed on dry Y, it gives a compound Z, used for disinfecting drinking water. Identify X, Y, G, and Z.
Q.14. A dry pellet of a common base B, when kept in the open, absorbs moisture and turns sticky. The compound is also a by-product of the Chlor-alkali process. Identify B. What type of reaction occurs when B is treated with an acidic oxide? Write a balanced chemical equation for one such solution.
Q.15. A sulfate salt of Group 2 element of the Periodic Table is a white, soft substance, which can be molded into different shapes by making its dough. When this compound is left in the open for some time, it becomes a solid mass and cannot be used for molding purposes. Identify the sulfate salt. Why does it show such behaviour? Give the reaction involved.
Q.16. Identify the compound X on the basis of the reactions given below. Also, write the name and chemical formula of A, B, and C.
Ans. ‘X ’ is NaOH.