Question

Suppose a group of volunteers is planning to build a park near a local lake. The lake is known to contain low levels of arsenic (As).(As). Therefore, prior to starting construction, the group decides to measure the current level of arsenic in the lake. If a 14.3 cm314.3 cm3 sample of lake water is found to have 159.5 ng As,159.5 ng As, what is the concentration of arsenic in the sample in parts per billion (ppb), assuming that the density of the lake water is 1.00 g/cm3?1.00 g/cm3?

Answer 1

The concentration of arsenic in the sample in parts per billion (ppb) is 11.1538 .

Step-by-step explanation:

Density of the lake water =
`1.00g/cm^3`

Amount of arsenic in 14.3
`cm^3` of water = 159.5 ng =
`1.595* 10^(-7) g`

Mass of the lake water:

`Mass=Density* volume=1.00 g/cm^3* 14.3 cm^3=14.3 g`

Concentration in parts per billion:

`\frac{\text{Mass of solute}}{\text{Mass of solution}}* 10^9`

`(1.595* 10^(-7) g)/(14.3 g)* 10^9=11.1538` parts per billion

The concentration of arsenic in the sample in parts per billion (ppb) is 11.1538.