Question

At 20°C, an aqueous solution that is 24.0% by mass in ammonium chloride has a density of 1.0674 g/mL. What is the molarity of ammonium chloride in the solution? The formula weight of NH4Cl is 53.50 g/mol.

Answer 1

Answer:

Molarity = 4.79 M

Explanation:

Mass percentage -

Mass percentage of A is given as , the mass of the substance A by mass of the total solution multiplied by 100.

i.e.

mass % A = mass of A / mass of solution * 100  

Given,

24% by mass of ammonium chloride,

so,

100 g solution contains , 24 g of ammonium chloride,

mass of solution = 100g

and mass of the solute , i.e. , ammonium chloride = 24 g .

Hence,

Moles -

Moles are calculated as the given mass divided by the molecular mass.  

i.e. ,

moles = ( mass / molecular mass )

Given,

The molecular mass of ammonium chloride is 53.50 g /mol

moles of ammonium chloride = 24 g / 53.50 g /mol

moles of ammonium chloride = 0.449 mol

Density -

Density of a substance is given as the mass divided by the volume ,

Density = mass / volume ,

Volume = mass / density

Given ,

Density of ammonium chloride = 1.0764 g /mL

Calculated above , mass of solution = 100 g

volume of solution = 100 g / 1.0764 g/ mL

volume of solution = 93.69 mL

Since , 1 ml = 1/1000 L

volume of solution = 93.69 /1000 L

volume of solution = 0.09369 L

Molarity -

Molarity of a solution is given by the moles of solute per liter of the solution

Hence,  

M = moles of solute / volume of solution (in L)

As calculated above,

moles of ammonium chloride = 0.449 mol

volume of solution = 0.09368 L

Putting in the above formula

Molarity = 0.449 mol / 0/09368 L

Molarity = 4.79 M

Answer 2

The molarity of ammonium chloride in the solution is 4.79 M

What is the molarity of a solution?

The number of moles of solute dissolved in one liter of solution is the molarity (M) of the solution.

Calculation of molarity:

Given,

The mass of the solution is 24.0%

Density is 1.0674 g/ml

The weight of NH4Cl is 53.50 g/mol

Step 1: Convert Mass % into gram

Considering the mass of solution = 100g

24% of 100g

Mass is 24 gram

Step 2: Calculate the mole compound

Moles = mass divided from molecular mass

The molecular mass of ammonium chloride is 53.50 g /mol

Thus,

$\bold{Moles = \dfrac{24}{53.50} = 0.449 mol}$

Step 3: Calculating the volume

$\bold{Volume = \dfrac{mass}{density} }$

$\bold{Volume = \dfrac{ 100}{1.0674 g/m} = 93.69 ml}$

$\bold{Volume\; of \;solution= \dfrac{ 93.69}{1000 L} = 0.09369 L}$

Step 4: Now, Molarity of the compound is

$\bold{Molarity = \dfrac{moles\; of\; solute}{volume\; of \;solution (in L)}}$

Mole of ammonium chloride = 0.449 mol

Volume of solution = 0.09368 L

By formula,

$\bold{Molarity = \dfrac{0.449 mol}{0.09368 L} = 4.79 m}$

Thus, the Molarity of ammonium chloride is  = 4.79 m.

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