Why do you have to have a certain number of reactants on one side?

Astudent carefully transfers 30 g of water and 30 g of alcohol in a glass tube, forming two layers and filling the tube completely. after sealing the tube, the student mixes the solutions, and notices a bubble that forms in the tube. what is the mass of the contents in the glass tube after mixing?

The minerals found in bones are deposited by living cells called

Can someone me with 3 and 4 plz. this is for masteries test.