select the correct answer. thomas has 235 grams of k₂s in the chemistry lab. how many atoms of potassium (k)…

Answer:

C. $2.57\times 10^{24}$

Explanation:

Step1: Calculate molar mass of $K_2S$

The molar mass of $K$ is $39.10\ g/mol$ and of $S$ is $32.07\ g/mol$. So molar mass of $K_2S$ is $2\times39.10 + 32.07=110.27\ g/mol$.

Step2: Calculate moles of $K_2S$

Moles of $K_2S=\frac{235\ g}{110.27\ g/mol}\approx 2.13\ mol$.

Step3: Determine moles of $K$

In $K_2S$, there are 2 moles of $K$ for every 1 mole of $K_2S$. So moles of $K = 2\times2.13\ mol = 4.26\ mol$.

Step4: Calculate number of $K$ atoms

Using Avogadro's number $N_A = 6.022\times 10^{23}\ atoms/mol$, number of $K$ atoms $=4.26\ mol\times6.022\times 10^{23}\ atoms/mol\approx2.57\times 10^{24}$ atoms.