Why is iron sulphide a compound?

Classify the following substances into compounds and mixtures :

Carbon dioxide, air, water, milk, common salt, blood, fruit juice, iron sulphide.

Give one example for the following type of mixture:

 solid-solid homogeneous mixture

Give one example for the following type of mixture:

 solid-liquid heterogeneous mixture

Give one example for the following type of mixture:

misicible liquids

Give one example for the following type of mixture:

liquid-gas homogeneous mixture

Suggest a suitable technique to separate the constituents of the following mixture. Also, give the reason for selecting the particular method.

Salt from seawater

Suggest a suitable technique to separate the constituents of the following mixture. Also, give the reason for selecting the particular method.

Ammonium chloride from sand

Suggest a suitable technique to separate the constituents of the following mixture. Also, give the reason for selecting the particular method.

Chalk powder from water