Question

Calculate the volume in mL of a solution required to provide the following:

(a) 2.44 g of sodium chloride from a 0.300 M solution

_____mL


(b) 7.30 g of ethanol from a 1.85 M solution

___mL


(c) 8.70 g of acetic acid (CH₃COOH) from a 0.626 M solution

____mL

Answer 1

a)

Molar mass of NaCl,

MM = 1*MM(Na) + 1*MM(Cl)

= 1*22.99 + 1*35.45

= 58.44 g/mol

mass,m = 2.44 g

number of mol,

n = mass/molar mass

= 2.44/58.44

= 0.0418 mol

Now use:

M = number of mol / volume in L

0.3 = 0.0418/ volume in L

volume = 0.139 L

volume = 139 mL

Answer: 139 mL

b)

Molar mass of C2H5OH,

MM = 2*MM(C) + 6*MM(H) + 1*MM(O)

= 2*12.01 + 6*1.008 + 1*16.0

= 46.068 g/mol

mass,m = 7.30 g

number of mol,

n = mass/molar mass

= 7.3/46.068

= 0.1585 mol

Now use:

M = number of mol / volume in L

1.85 = 0.1585/ volume in L

volume = 0.086L

volume = 86 mL

Answer: 86 mL

c)

Molar mass of C2H4O2,

MM = 2*MM(C) + 4*MM(H) + 2*MM(O)

= 2*12.01 + 4*1.008 + 2*16.0

= 60.052 g/mol

mass,m = 8.70 g

number of mol,

n = mass/molar mass

= 8.7/60.052

= 0.1449 mol

Now use:

M = number of mol / volume in L

0.626 = 0.1449/ volume in L

volume = 0.231 L

volume = 231 mL

Answer: 231 mL