Chemical Reactions and Equations — Science STD 10 — Question

Iqbal treated a lustrous, divalent element M with sodium hydroxide. He observed the formation of bubbles in reaction mixture. He made the same observations when this element was treated with hydrochloric acid. Suggest how can he identify the produced gas. Write chemical equations for both the reactions.

Explain how, a reduction reaction of aluminium can be used for welding cracked machine parts of iron. Write a chemical equation for the reaction involved.

A metal combines with a non-metal by the transfer of electrons to form a compound Y.

1. State the type of bonds in Y.
2. What can you say about its melting point and boiling point?
3. Will it be a good conductor of electricity?
4. Will it dissolve in an organic solvent or not?

What are homologous series of carbon compounds? Write the molecular formula of two consecutive members of homologous series of aldehydes. State which part of these compounds determines their (i) physical and (ii) chemical properties.

When zinc metal is treated with a dilute solution of a strong acid, a gas is evolved, which is utilised in the hydrogenation of oil. Name the gas evolved. Write the chemical equation of the reaction involved and also write a test to detect the gas formed.

Give reasons for the following observations:

1. Air holes of a gas burner have to be adjusted when the vessels being heated get blackened by the flame.
2. Use of synthetic detergents causes pollution of water.

Explain why, an aqueous solution of sodium chloride is not used for the electrolytic extraction of sodium metal.

A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.

1. Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved.
2. Name the black substance formed and give its chemical formula.

Using electron-dot diagrams which show only the outermost shell electrons, show how a molecule of nitrogen, N, is formed from two nitrogen atoms. What name is given to this type of bonding? (Atomic number of nitrogen is 7)

The atomic number of an element is 12.

1. Write its electronic configuration and determine its valency.
2. Is it more reactive or less reactive than Ca (atomic number 20)? Justify your answer giving reason.
3. Is it a metal or a non-metal?
4. Write the formula of its oxide.