How many moles of K2SO4 are in 15.0 grams of K2SO4

2 answers:

5 0

Molar mass K₂SO₄ = 174.259 g/mol

$n = \frac{m}{M}$

$n = \frac{15.0 g}{174.259g/mol}$

$n = 0.0860$ moles

hope this helps!

IrinaVladis [17]3 years ago

5 0

$\boxed{{\text{0}}{\text{.0860 mol}}}$ of ${{\text{K}}_2}{\text{S}}{{\text{O}}_4}$ is present in 15 g of ${{\text{K}}_2}{\text{S}}{{\text{O}}_4}$ .

Further explanation:

Amount of substance is measured in terms of mole. The mass of substance with same number of fundamental units as atoms in 12 g of carbon 12 is 1 mole.

In step 1, we have to calculate the molar mass of ${{\text{K}}_2}{\text{S}}{{\text{O}}_4}$ . The molar mass of ${{\text{K}}_2}{\text{S}}{{\text{O}}_4}$ can be calculated by using equation (1).

Step 1: The molar mass of ${{\text{K}}_2}{\text{S}}{{\text{O}}_4}$ is calculated as follows:

${\text{Molar mass of}}{\mathbf{ }}{{\text{K}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}} = \left[ \begin{gathered}{\text{2}}\left( {{\text{Atomic mass of K}}} \right)+\hfill\\{\text{1}}\left({{\text{Atomic mass of S}}} \right)+\hfill\\{\text{4}}\left({{\text{Atomic mass of O}}}\right)\hfill\\\end{gathered}\right]$

…… (1)

The atomic mass of K is 39.09 g.

The atomic mass of S is 32.06 g.

The atomic mass of O is 16 g.

Substitute these values in equation (1).

$\begin{aligned}{\text{Molar mass of}}{\mathbf{ }}{{\text{K}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}&=\left[{{\text{2}}\left({{\text{39}}{\text{.09 g}}}\right)+{\text{1}}\left({{\text{32}}{\text{.06 g}}}\right)+{\text{4}}\left({{\text{16 g}}}\right)}\right]\\&=\left[{{\text{78}}{\text{.18 g}}+{\text{32}}{\text{.06 g}}+{\text{64 g}}}\right]\\&=174.24\;{\text{g/mol}}\\\end{gathered}$

In step 2, the molar mass calculated in step 1 is used to calculate the number of moles of ${{\text{K}}_2}{\text{S}}{{\text{O}}_4}$ . The number of moles of ${{\text{K}}_2}{\text{S}}{{\text{O}}_4}$ is calculated by using equation (2).

Step 2: The formula to calculate the moles of ${{\text{K}}_2}{\text{S}}{{\text{O}}_4}$ is as follows:

${\text{Moles of }}{{\text{K}}_2}{\text{S}}{{\text{O}}_4}{\mathbf{=}}\frac{{{\text{Given mass of}}{\mathbf{ }}{{\text{K}}_2}{\text{S}}{{\text{O}}_4}}}{{{\text{Molar mass of}}{\mathbf{ }}{{\text{K}}_2}{\text{S}}{{\text{O}}_4}}}$

…… (2)

The given mass of ${{\text{K}}_2}{\text{S}}{{\text{O}}_4}$ is 15 g.

The molar mass of ${{\text{K}}_2}{\text{S}}{{\text{O}}_4}$ is 174.24 g/mol.

Substitute these values in equation (2).

$\begin{aligned}{\text{Moles of }}{{\text{K}}_2}{\text{S}}{{\text{O}}_4}&=\left( {15\;{\text{g}}}\right)\left({\frac{{1\;{\text{mol}}}}{{174.24\;{\text{g}}}}}\right)\\&={\text{0}}{\text{.086088}}\\&\approx{\mathbf{0}}{\mathbf{.0860}}\;{\mathbf{mol}}\\\end{aligned}$