Question

A 1.00 L sample of water contains 0.0048 g of SH ions. Determine the concentration (in ppm) of SH ions? The density of the solution is 1.00 g/mL.

and

What is the weight percent of a caffeine solution prepared by dissolving 6.35 g of caffeine, C8H10N4O2, in 75.0 g of benzene, C6H6?

Answer 1

1)

given

mass of SH ions = 0.0048 g

we know that

1 g = 1000 mg

so

mass of SH ions = 0.0048 x 1000 mg

mass of SH ions = 4.8 mg

given

volume = 1 L

we know that

concentration in ppm = mass of SH ions in mg / volume of solution in L

concentration in ppm = 4.8 / 1

concentration in ppm = 4.8

so

the concentration of SH ions is 4.8 ppm

2)

now

total mass of the solution = mass of caffeine + mass of benzne

total mass of the solution = 6.35 + 75

total mass of the solution = 81.35 g

now

% weight of caffeine = mass of caffeine x 100 / mass of solution

% weight of caffeine = 6.35 x 100 / 81.35

% weight of caffeine = 7.8

so

the weight percent of caffeine solution is 7.8%