What happens when dilute hydrochloric acid is added to iron fillings ? Tick the correct answer.

What do you mean by a precipitation reaction? Explain by giving examples.

Write the balanced equation for the following chemical reactions.

$(i)$ Hydrogen $+$ Chlorine $\to $ Hydrogen chloride

$(ii)$ Barium chloride $+$ Aluminium sulphate $\to $ Barium sulphate $+$ Aluminium chloride

$(iii)$ Sodium $+$ Water $\to $  Sodium hydroxide $+$ Hydrogen

Translate the following statements into chemical equations and then balance them.

$(a)$ Hydrogen gas combines with nitrogen to form ammonia.

$(b)$ Hydrogen sulphide gas burns in air to give water and sulpur dioxide.

$(c)$ Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.

$(d)$ Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

Explain the "Reduction'' in terms of gain or loss of oxygen with two examples.