Chemists often use molarity M , in m o l e s / l i t e r , to measure the concen

Question

Chemists often use molarity M, in moles/liter, to measure the concentration of solutions. Molarity is a common unit of concentration because the volume of a liquid is very easy to measure. However, the drawback of using molarity is that volume is a temperature-dependent quantity. As temperature changes, density changes, which affects volume. Volume markings for most laboratory glassware are calibrated for room temperature, about 20?C.

Fortunately, there are several other ways of expressing concentration that do not involve volume and are therefore temperature independent.

A 2.600

Explanation / Answer

1. mass of water = 999.3*0.9982 = 997.50126 g = 0.997kg

molality = 0.026/ 0.997 = 0.02607m

2.) moles of water = 997.50126/18 = 55.416moles

moles of NaCl = 0.026*1 = 0.026 moles

mole fraction = 0.026/(0.026+55.416) = 0.04%

3.) mass of NaCl = 0.026*58.5 = 1.521g

mass% = 1.521/(1.521+997.501) = 0.152%

4.) conc. on ppm = 1000000 * 1.521/997.501 = 1524.8105 ppm

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