A sodium sulfate solution is measured at 13 molal in pure water at a source comp

Question

A sodium sulfate solution is measured at 13 molal in pure water at a source company. (sodium sulfate molar mass = 142.05 g mol^-1) The lab needs to report the concentration in molarity. What is the final molarity of the sodium sulfate solution? (density of water = 1.0 g mL^-1 ; density of the solution = 1.4 g mL A. 1.3 M B. 0.18 M C. 1.8M D. 1.5 M E. 0.78 M What is the osmotic pressure of a solution that contains 15.5 g of butyl alcohol (molar mass = 74. 12 g mol^-1) dissolved in enough water to make a 600.0 mL solution at 27.0 degree C? A. 9.7 atm B. 5.6 atm C. 8.6 atm D. 8.8 torr E. 7.0 atm

Explanation / Answer

32)

32)

consider 1 kg os solvent

use:

molality = number of mol of solute / mass of solvent in Kg

1.3 = n / 1 Kg

n = 1.3 mol

molar mass of Na2SO4 = 142.05 g/mol

so,

mass of Na2SO4 = number of mol * molar mass

= 1.3 mol * 142.05 g/mol

= 184.7 g

mass of solution = mass of solvent + mass of solute

= 1000 g + 184.7 g

= 1184.7 g

density of solution = 1.4 g/mL

So,

volume of solution = mass of solution /density of solution

= 1184.7 g / 1.4 g/mL

= 846.2 mL

= 0.8462 L

Molarity = number of mol of solute / mass of solvent in Kg

= 1.3 mol / 0.8462 L

= 1.5 M

Answer: D

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