A gas mixture contains 75.2\% nitrogen and 24.8\% krypton by

$$n_{N_2}=\begin{array}{cc}75.2g{N}^2& 1mol{N}^2\\ & 28.0134g{N}^2\end{array}$$ Each percentage represents the number of grams of an element per 100.0 grams of that gas mixture. Convert these masses to moles using molar masses.
${\displaystyle =2.6844mol{N}^2}$
$$n_{Kr}=\begin{array}{cc}24.8gKr& 1molKr\\ & 83.798gKr\end{array}$$
${\displaystyle =0.29595molKr}$
Use the mole fraction equation to determine the partial pressure of krypton
${\displaystyle P_{Kr}=X_{Kr}{P}_{\to t}}$
${\displaystyle =\left(\frac{n_{Kr}}{n_{Kr}+n_{N^2}}\right)P_{\to t}}$
${\displaystyle =\left(\frac{0.29595mol}{0.29595mol+2.6844mol}\right)\left(745mmHg\right)}$
${\displaystyle =74.0mmHg}$

Step 1
Given data
A gas mixture contains -
Nitrogen ${\displaystyle =75.2\mathrm{\%}}$
krypton ${\displaystyle =24.8\mathrm{\%}}$
total pressure is 745 mmHg.
Step 2
Solution-
calculate the mole fraction of the component-
Mole fraction of tha erypton —
$X_2=\frac{molesofthecrypton}{totalmolesofthe3gasmixture}$
${\displaystyle X_2=\frac{0.296mol}{(2.68+0.296)mol}=0.0995}$
partial pressure of the crypton:
total pressure x mole fraction of the crypton
${\displaystyle 745mmHg\times 0.0995=74.12mmHg}$

Step 1
Given:
Mass of nitrogen =75.2 g (75.2% by mass)
Mass of krypton =24.8 g (24.8% by mass)
Total pressure =745 mm Hg
Step 2
To determine the partial pressure of krypton as follows,
Molar mass of nitrogen =28.02$\frac{g}{mol}$
Calculating the moles of nitrogen using the formula,
$n_1=\frac{Massofnitrogen}{Molarmassofnitrogen}$
$=\frac{75.2g}{28.02\frac{g}{mol}}$
=2.68mol
Molar mass of krypton =83.80$\frac{g}{mol}$
Calculating the moles of krypton using the formula,
Mass of krypton
$n_2=\frac{Massofkrypton}{Molarmassofkrypton}$
$=\frac{24.8g}{83.80\frac{g}{mol}}$
=0.296mol
Step 3
To calculate the mole fraction of krypton,
Moles of krypton, $X_2=\frac{Molesofthecrypton}{Totalmolesofgasmixture}$
$=\frac{0.296mol}{(2.68+0.296)mol}=0.0995$
Partial pressure of krypton =Total pressure * Mole fraction of krypton
Substituting the values in the above formula,
Partial pressure of krypton =745mmHg*0.0995=74.1mmHg
Hence, the partial pressure of krypton in the given mixture is 74.1mmHg .