Question

1)CALCULATE MOLARITY OF EACH SOLUTION!Show work.

a) 3.00 MOL NaCl in 400.0 mLsolution.

b) 0.600 mol KNO3 IN 100.0 mL solutiom

c) 14.2g NaSO4 in 50.0 mL solution

d) 20.0g CaCO in 200.0 mL solution

2)Calculate # of moles in each solution.

a) 200.0 mL of .300M solution

b) 40.0 mL of a 5.00 solution

3) Calculate the # g of solute needed to make

a)100.0 mL of .200M NaCl solution

b)50.0mL of .600M K2SO4 solution

c)300.0 mL of .400M CaF2 solution

d)20.0 mL of .100 Mg(NO3)2 solution

Answer 1

1)

a)

volume , V = 4*10^2 mL

= 0.4 L

use:

Molarity,

M = number of mol / volume in L

= 3/0.4

= 7.5 M

Answer: 7.50 M

b)

volume , V = 1*10^2 mL

= 0.1 L

use:

Molarity,

M = number of mol / volume in L

= 0.6/0.1

= 6 M

Answer: 6.0 M

c)

Molar mass of Na2SO4,

MM = 2*MM(Na) + 1*MM(S) + 4*MM(O)

= 2*22.99 + 1*32.07 + 4*16.0

= 142.05 g/mol

mass(Na2SO4)= 14.2 g

use:

number of mol of Na2SO4,

n = mass of Na2SO4/molar mass of Na2SO4

=(14.2 g)/(1.421*10^2 g/mol)

= 9.996*10^-2 mol

volume , V = 50 mL

= 5*10^-2 L

use:

Molarity,

M = number of mol / volume in L

= 9.996*10^-2/5*10^-2

= 1.999 M

Answer: 2.00 M

d)

Molar mass of CaCO3,

MM = 1*MM(Ca) + 1*MM(C) + 3*MM(O)

= 1*40.08 + 1*12.01 + 3*16.0

= 100.09 g/mol

mass(CaCO3)= 20.0 g

use:

number of mol of CaCO3,

n = mass of CaCO3/molar mass of CaCO3

=(20 g)/(1.001*10^2 g/mol)

= 0.1998 mol

volume , V = 2*10^2 mL

= 0.2 L

use:

Molarity,

M = number of mol / volume in L

= 0.1998/0.2

= 0.9991 M

Answer: 1.00 M

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