Question

A saline solution contains 1.1% NaCl by mass. How much NaCl is present in 87.2 g of this solution?

Answer 1

This is not the answer but it the same thing:

1.3 g / 100 g = 0.013.
0.013 * 89.2 g = 1.1596 g
= 1.16 g.

Answer 2

Or, another way.
1.1% w/w means 1.1g NaCl in 100 g solution.
You want to know how much is there in 87.2 g (and not 100g); therefore,
1.1 x (87.2/100) = ?

Answer 3

A 5.00-ml sample of a H3PO4 solution of unknown concentration is titrated with a 0.1003 M NaOH solution. A volume of 6 .55ml of the Na OH solution was required to reach the endpoint. What is the concentration of the unknown H3PO4 solution?