Question

Determine the boiling point of a solution if the molality of a non-ionizing and non-volatile solute was 0.592 mol/kg. (The boiling point elevation constant for water is 0.51oC/m.)

Determine the freezing point of a solution is the molality of a non-ionizing solute was 0.467 mol/kg. (The freezing point depression constant for water is 1.86 ^oC/m.)

What is the mole fraction of Compound A in a mixture containing 2.56 g of compound A (MM = 175.4 g/mol) and 5.7 g of Compound B(MM = 216.1g/mol)?

What is the molality of Compound A in a solution containing 8.98 g of Compound A(MM = 110.4 g/mol) and 98.86 g of water (MM = 18.0 g/mol)?

Determine the molarity when 21.9 g of Compound A (MM = 148.8 g/mol) are dissolved into enough water to make a solution of 684 mL. (Do not include units.)

What is the percent by mass of copper in an alloy containing 3.35 g of copper and 7.47 g of nickel?

What is the mass of a compound needed to make a 249.0 mL of a solution with a molarity of 4.67 M? The molar mass of the compound is 156.9 g/mol. (Do not include units)

Answer 1

Q. Determine the boiling point of a solution if the molality of a non-ionizing and non-volatile solute was 0.592 mol/kg. (The boiling point elevation constant for water is 0.51oC/m.)
Soln: Using the relation for elevation of boiling point:

       where = elevation of boing point, =boiling point elevation constant , m =molality

m = 0.3019

Thus, the boiling point of a solution is (100+0.3016)=100.3019 .

Q. Determine the freezing point of a solution is the molality of a non-ionizing solute was 0.467 mol/kg. (The freezing point depression constant for water is 1.86 oC/m.)
Soln: Using the relation for depression of freezing point:

where = depression of freezing point, = freezing point depression constant , m =molality

m = 0.868

Thus, the freezing point of a solution is (0-0.868)= -0.868 .

Q. What is the mole fraction of Compound A in a mixture containing 2.56 g of compound A (MM = 175.4 g/mol) and 5.7 g of Compound B(MM = 216.1g/mol)?
Soln: Moles of compound A =2.56 g /175.4 g/mol= 0.0146
         moles of compound B=5.7 g/216.1g/mol= 0.0264
         So, mole fraction of A = moles of A/ (moles of A+moles of B)= 0.0146/0.041 = 0.356

Q. What is the molality of Compound A in a solution containing 8.98 g of Compound A(MM = 110.4 g/mol) and 98.86 g of water (MM = 18.0 g/mol)?
Soln: Molality of compound A = moles of compound A/ mass of solvent (in kg) = (8.98g/110.4g/mol)/0.09886 g

          = 0.823 m

Q. Determine the molarity when 21.9 g of Compound A (MM = 148.8 g/mol) are dissolved into enough water to make a solution of 684 mL. (Do not include units.)
Soln: Mass of 684 ml of water = 684 g (density= 1kg/m^3)
         Molality of compound A = moles of compound A/ mass of solvent (in kg) = (21.9g/148.8g/mol)/0.684 g

         = 0.215 m

Q. What is the percent by mass of copper in an alloy containing 3.35 g of copper and 7.47 g of nickel?
Soln: Mass % = (mass of copper in the alloy/total mass of alloy)*100 = {3.35g/(3.35+7.47)}*100=30.96%

Q. What is the mass of a compound needed to make a 249.0 mL of a solution with a molarity of 4.67 M? The molar mass of the compound is 156.9 g/mol. (Do not include units)
Soln: Molarity= moles of solute/volue of solution in Ltr
         4.67 M = moles of solute/0.249 Ltr
        Moles of solute= 1.1628= mass of compound/156.9 g/mol
        Thus, mass of compound= 1.1628mol*156.9g/mol = 182.45 g