Name the element used as a standard for atomic mass scale.

What is meant by saying that ‘the molecular mass of oxygen is 32’?

Fill in the following blanks with suitable words:

(a) In water, the proportion of oxygen and hydrogen is …….. by mass.

(b) In a chemical reaction, the sum of the masses of the reactants and the products remains unchanged. This is called ………… .

Which particular atom of the above element is used for this purpose?

What value has been given to the mass of this reference atom?