Question

"Hard" water in parts of the Midwest may have a calcium ion concentration as high as 400 ppm. What is this calcium ion concentration when expressed as a percentage?

A: 40%
B: 4%
C: 0.4%
D: 0.04%

Answer 1

The calcium ion concentration of 400 ppm when expressed as a percentage is 0.04%.

Step-by-step explanation:

The calcium ion concentration of 400 ppm (parts per million) when expressed as a percentage is calculated as follows: To express this concentration as a percentage, we need to convert ppm to a decimal and then multiply by 100.

To convert from ppm to percent, you divide by 10,000, because 1% is the same as 10,000 ppm
400 ppm / 10,000 = 0.04%

Therefore, a concentration of 400 ppm as a percentage is 0.04%.