A 11.97g sample of NaBr contains 22.34 % Na by mass. Considering the law of constant composition (definite proportions), how many grams of sodium does a 9.51g sample of sodium bromide contain?

2.125 g

Explanation:

We have;

Mass of NaBr sample is 11.97 g % composition by mass of Na in the sample is 22.34%

We are required to determine the mass of 9.51 g of a NaBr sample.

Based on the law of of constant composition, a given sample of a compound will always contain the sample percentage composition of a given element.

In this case,

A sample of 11.97 g of NaBr contains 22.34% of Na by mass Therefore;

A sample of 9.51 g of NaBr will also contain 22.345 of Na by mass

But;

% composition of an element by mass = (Mass of element : mass of the compound) * 100

Therefore;

Mass of the element = (% composition of an element * mass of the compound) : 100

Therefore;

Mass of sodium = (22.34% * 9.51 g) : 100

= 2.125 g

Thus, the mass of sodium in 9.51 g of NaBr is 2.125 g