1. What is the Molarity of an 8.02 m NH 3 solution which has a density of 0.950

Question

1. What is the Molarity of an 8.02 m NH3 solution which has a density of 0.950 g/mL?

2. How many moles of hydrogen peroxide, H2O2 , are present in 25.0 g of a 3% solution?

3. The density of an aqueous solution containing 12.50 g K2SO4 in 100.00 g of solution is 1.083 g/mL. Calculate the concentration of this solution in terms of Molarity of K2SO4 , molality of K2SO4 , mass % of K2SO4 , and mole fraction of solvent.

4. What is the vapor pressure, in mmHg, of a solution of 5.67 g glucose, C6H12O6 , dissolved in 25.2 g water at 25 ºC?

5. Assuming ideal behavior, what is the freezing point of a 0.030 m solution of Al2(SO4)3 ?

Answers:

1. 6.70 M

2. 0.0221 moles

3. 0.7767 M, 0.8197 m, 12.50 %, 0.9854 mole fraction

4. 23.3 mmHg

5. -0.28 ºC

Explanation / Answer

1. m = M*1000/((d*1000)-(M*Mwt of solvent))

8.02 = M*1000/((0.95*1000)-(M*17))

MoLARITY   = 6.7 M

2.

mass OF H2O2 = 25*3/100 = 0.75 grams

moles of hydrogen peroxide, H2O2 = w/mwt = 0.75/34 = 0.0221 mole

3.

Molar mass K2SO4 = 174.259 g/mol

Molarity of K2SO4 = (12.5/174.259)*(1000/(100/1.083))

         
           = 0.7767 M

molality of K2SO4 = (12.5/174.259)*(1000/(100-12.5)) = 0.8197 m

mass % of K2SO4 = 12.5/100*100 = 12.5%

molefraction of solven = (87.5/18)/((87.5/18)+(12.5/174.259))

   = 0.985

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