Ch 202 Problem 13.36

a) What is the mass in percentage of iodine, I₂, in a solution containing 0.035 mol I₂

in 115 g of CCl₄?

The mass per cent of a component in a solution is given by

Mass % of component = (mass of component / total mass of solution) x 100

so, mass % of I₂ = (mass of I₂ in solution / total mass of solution) x 100

to find the mass of I₂, convert 0.035 mol I₂ to grams; the molecular weight of I₂ is 253.809 gm/mol

now, the mass % I₂ is given by the mass of I₂ / total mass (including the mass of the I₂!!!)

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(b) Seawater contains 0.0079 g of Sr²⁺ per kilogram of water. What is the concentration of Sr²⁺ in ppm?

note that

ppm = (mass of component in solution / total mass of solution) x 1.0x10⁶

from the info in the problem, we have the mass of Sr²⁺ and the total mass of the solution

(1 kg). We just divide (like in part a) and multiply x 10⁶ to get ppm.

DAC 7/7/08