Question

Be sure to answer all parts.
Calculate the molarity of each of the following solutions:
(a) 28.5 g of ethanol (C2H5OH) in 4.50 x 102 mL of solution
M M
es
(b) 21.6 g of sucrose (C12H22011) in 67.0 mL of solution
M
(c) 6.65 g of sodium chloride (NaCl) in 96.2 mL of solution
M

Answer 1

Answer: The molarity of each of the given solutions is:

(a) 1.38 M

(b) 0.94 M

(c) 1.182 M

Explanation:

Molarity is the number of moles of a substance present in liter of a solution.

And, moles is the mass of a substance divided by its molar mass.

(a) Moles of ethanol (molar mass = 46 g/mol) is as follows.

$Moles = \frac{mass}{molar mass}\\= \frac{28.5 g}{46 g/mol}\\= 0.619 mol$

Now, molarity of ethanol solution is as follows.

$Molarity = \frac{moles}{Volume (in L)}\\= \frac{0.619 mol}{4.50 \times 10^{2} \times 10^{-3}L}\\= 1.38 M$

(b) Moles of sucrose (molar mass = 342.3 g/mol) is as follows.

$Moles = \frac{mass}{molar mass}\\= \frac{21.6 g}{342.3 g/mol}\\= 0.063 mol$

Now, molarity of sucrose solution is as follows.

$Molarity = \frac{moles}{Volume (in L)}\\= \frac{0.063 mol}{0.067 L} (1 mL = 0.001 L)\\= 0.94 M$

(c) Moles of sodium chloride (molar mass = 58.44 g/mol) are as follows.

$Moles = \frac{mass}{molar mass}\\= \frac{6.65 g}{58.44 g/mol}\\= 0.114 mol$

Now, molarity of sodium chloride solution is as follows.

$Molarity = \frac{moles}{Volume (in L)}\\= \frac{0.114 mol}{0.0962 L}\\= 1.182 M$

Thus, we can conclude that the molarity of each of the given solutions is:

(a) 1.38 M

(b) 0.94 M

(c) 1.182 M