Molecule of water contains hydrogen and oxygen in a 1: 8 ratio by mass. this is a statement of ) the law of multiple proportions. b) the law of constant composition. c) the law of conservation of mass. d) the law of conservation of energy. e) none of the above.

The correct answer is B.

Explanation:

The molecule of water has 2 atoms of hydrogen and 1 atom of oxygen.

The ratio of masses are given as:

This illustrates the law of definite proportions which is also known as law of constant compositions .

The law states that 'the elements combining to form compound always combine in a fixed ratio by their mass.'

Whereas :

Law of multiple proportion states that when two elements combine with each other to form more than one compounds , the mass of one element with respect to the fixed mass of another element are in ratio of small whole numbers.

Law of conservation of mass states that mass can neither be created nor be destroyed but it can only be transformed from one form to another form.

In a balanced chemical reaction ,total mass on the reactant side must be equal to the total mass on the product side.

Law of conservation of energy states that energy can neither be created nor be destroyed but it can only be transformed from one form to another form.

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%