Unit - 3.1 Elements and Compounds — CHEMISTRY STD 7 — Question

For the following statements, say whether it describes a solid, a liquid or a gas.
Particles are far apart and move in all directions

Give a balanced equation to obtain oxygen from Lead dioxide.

Statements given below are incorrect. Write the correct statements :
Soda water is prepared by dissolving washing soda in water.

Name the gas evolved when sodium carbonate is added to dilute hydrochloric acid.

Write symbolic representation for the following word equation and balance them :
Calcium carbonate → Calcium oxide + Carbon dioxide.

Answer the question put against the following constituents of air :
Carbon dioxide : “Although carbon dioxide plays no role in respiration, all life would come to an end if there is no carbon dioxide in air.” Support this statement with relevant facts.

Elements X and Y have 1 and 7 electrons in their outermost shell respectively.
Which will form positive ion?

Define: Atomic weight :

Define:- Radicals