Question

A single 250 gram

serving of one sports drink contains
0.055 grams of sodium ions. What is the
concentration of sodium ions expressed
as % by mass?
2.2 x 10-4
2.2 x 102
2.2 x 10-2
2.2 x 10-4

Answer 1

2.2 x 10^-2

0.055 / 250 = 0.00022 - This would be 2.2 x 10^-4, but the question is asking for percent, not proportion, so multiply by 100% to get the percentage.

0.00022 * 100% = 0.022% = 2.2 * 10^-2