Question

Which of the following is a mixture ? a) Air b) helium gas c) carbon dioxide d) oxygen​

Answer 1

a) Air

Air is the invisible mixture of gases that surrounds the Earth. Air contains important substances, such as oxygen and nitrogen, that most species need to survive. ... Standard Dry Air is made up of nitrogen, oxygen, argon, carbon dioxide, neon, helium, krypton, hydrogen, and xenon.

Answer 2

Answer:-

Which of the following is a mixture?

•Air

•Helium

•Gas

•carbon dioxide

•Oxygen

correct options is :- Air

A mixture consists of constituents in indefinite proportion . It may change over time.Air has 78% Nitrogen, 21% Oxygen and 1% other constituents such as CO2, water vapour etc. About 100 years ago proportion of CO2 in air was about 0.029% and now it is 0.035% .Thus we see that it's proportion has changed therefore , air is a mixture.