Acids, Bases and Salts — Science STD 10 — Question

On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, white precipitate is obtained.

1. Write a balanced chemical equation of the reaction involved.
2. What other name can be given to this precipitation reaction?
3. On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why?

The atomic number of an element is 19.

1. Write the electronic configuration of this element and determine (i) the valency of this element, and (ii) whether this element is a metal or a non-metal.
2. Write the formula of the oxide of this element.
3. Is this element more reactive or less reactive than Na (atomic number 11)? Justify your answer giving example.

A sulphate salt of Group 2 element of the Periodic Table is a white, soft substance, which can be moulded into different shapes by making its dough. When this compound is left in open for some time, it becomes a solid mass and cannot be used for moulding purposes. Identify the sulphate salt and why does it show such a behaviour? Give the reaction involved.

Differentiate between saturated and unsaturated hydrocarbons.

What is meant by isomers? Draw the structures of two isomers of butane, C₄H₁₀. Explain why we cannot have isomers of first three members of alkane series.

For making cake, baking powder is taken. If at home your mother uses baking soda instead of baking powder in cake,

1. How will it affect the taste of the cake and why?
2. How can baking soda be converted into baking powder?
3. What is the role of tartaric acid added to baking soda?

During extraction of metals, electolytic refining is used to obtain pure metals.

1. Which material will be used as anode and cathode for refining of silver metal by this process?
2. Suggest a suitable electrolyte also.
3. In this electrolytic cell, where do we get pure silver after passing electric current?

State one characteristic each of the chemical reaction which takes place when:
i. Dilute hydrochloric acid is added to sodium carbonate.
ii. Lemon juice is added gradually to potassium permanganate solution.
iii. Dilute sulphuric acid is added to the barium chloride solution.
iv. Quick lime is treated with water.
v. Wax is burned in the form of a candle.

2mL of sodium hydroxide solution is added to a few pieces of granulated zinc metal taken in a test tube. When the contents are warmed, a gas evolves which is bubbled through a soap solution before testing. Write the equation of the chemical reaction involved and the test to detect the gas. Name the gas which will be evolved when the same metal reacts with dilute solution of a strong acid.

Why should the metal sulphides and carbonates be converted to metal oxides in the process of extraction of metal from them?