Atoms, Molecules and Radicals — CHEMISTRY STD 7 — Question

State the use of manganese dioxide in the laboratory prepa-ration of oxygen from potassium chlorate.

A certain particle ‘X’ has 17 protons, 18 electrons and 20 neutrons.
What is the mass number of X ?

What happens when potassium nitrate is heated ?

Write the formulae of following salts by criss-cross method:-Potassium sulphate

State whether the following is physical or chemical changes.
passing electric current through a heater rod —

What is the importance of dissolved carbon dioxide and oxygen in water ?

Name two methods by which solid-solid mixtures can be separated.

Define:- Radicals

Write your observation for the following chemical reaction and name the product formed :
When manganese dioxide is added to potassium chlorate and heated.