Question

A brown substance X which is used for making electric wires when heated strongly turns black when hydrogen pass gas passes over the black substance it Regan its original colour name the reaction involved

Answer 1

Explanation:

Given -

• A Brown substance X is used for making electric wires.
• When X is heated strongly in presence of air it turns Black.
• When hydrogen gas is passed over the black substance it regain its original colour.
• The reddish brown coloured metal is copper metal (Cu).

To Find -

• The Brown substance X.
• The black coloured substance.

As we know that :-

Copper (Cu) is Brown coloured substance which is used to making electric wires.

Now,

When copper metal is heated in air, it forms black coloured substance . This black coloured compound is copper(II)oxide (CuO).

Chemical equation :-

• 2Cu + O2 →→heat→→ 2CuO

And

When hydrogen gas is passed over the black substance, i.e, CuO it turns into Cu and regains its original colour.

Chemical equation :-

• CuO + H2 → Cu+H2O

Hence,

The Brown substance X is Cu

Black coloured substance is CuO

This is the example of combination reaction.

Additional information :-

Types of chemical reaction :-

• Combination reaction -

Those reaction in which two or more substances combined to form a single substance, are called combination reaction.

Example -

C + O2 → CO2

• Decomposition reaction -

Those reaction in which a compound splits up into two or more simpler substances are known as decomposition reaction.

Example -

CaCO3 → CaO + CO2

• Displacement reaction -

Those reaction in which one element takes the place of another element in a compound, are known as Displacement reaction.

Example -

CuSO4 + Zn → ZnSO4 + Cu

• Double Displacement reaction -

Those reaction in which two compounds react by an exchange of ions to form two new compounds are called double displacement reaction.

Example -

AgNO3 + NaCl → AgCl + NaNO3