Question

Select the correct answer. Thomas has 235 grams of K2S in the chemistry lab. How many atoms of potassium (K) are in 235 grams of the compound? A. 2. 13 × 1023 B. 4. 26 × 1023 C. 2. 57 × 1024 D. 3. 37 × 1024 E. 7. 08 × 1024.

Answer 1

Atoms are the smallest division of the element. The potassium atoms present in the 235 gm of the compound is $2.57 \times 10^{24}$ atoms.

What is the number of atoms?

Given,

• Mass (m) of Potassium sulfide $(\rm K_{2}S)$ = 235 gm
• Molar mass (M) of  Potassium sulfide = 110.26 g/mol

Calculate the number of moles as:

$\begin{aligned}\rm Moles (n) &= \dfrac{\rm mass}{\rm molar\;\rm mass}\\\\&= \dfrac{235}{110.26}\\\\&=2.13\;\rm mol\end{aligned}$

In the given compound $\rm K_{2}S$, there are two atoms of potassium and one atom of sulphur.

If, 1 mole = $2 \times 6.022 \times 10^{23}$ atoms of potassium

Then, 2.13 moles = X atoms

Solving for X:

$2.13 \times 2 \times 6.022 \times 10^{23} = 2.57 \times 10^{24}$

Therefore, option c. $2.57 \times 10^{24}$ is correct.

Learn more about atoms here:

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