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Ch.13 - Solutions
Chapter 13, Problem 57

A hard water sample contains 0.0085% Ca by mass (in the form of Ca2+ ions). How much water (in grams) contains 1.2 g of Ca? (1.2 g of Ca is the recommended daily allowance of calcium for adults between 19 and 24 years old.)

Verified step by step guidance
1
Identify the percentage of calcium in the water sample, which is given as 0.0085% by mass.
Understand that this means there are 0.0085 grams of calcium in every 100 grams of water.
Set up a proportion to find out how many grams of water contain 1.2 grams of calcium. Use the relationship: (0.0085 g Ca / 100 g water) = (1.2 g Ca / x g water).
Solve the proportion for x, which represents the mass of water that contains 1.2 grams of calcium.
Rearrange the equation to solve for x: x = (1.2 g Ca * 100 g water) / 0.0085 g Ca.