Question

q.9. how many moles of k are there in 36.70 g of k? ans. given: 36.70 g find: mol k conceptual plan: solve: q.10. how many atoms of gold are there in 15.00 g of pure gold? (atomic mass of gold, au = 197.0 g/mol) ans.sort: given: find: conceptual plan: solve:

Explanation:

Step1: Recall molar - mass of K

The molar mass of potassium (K) is 39.10 g/mol.

Step2: Use mole - mass formula

The formula to calculate the number of moles $n$ is $n=\frac{m}{M}$, where $m$ is the mass and $M$ is the molar mass. Given $m = 36.70$ g and $M=39.10$ g/mol, then $n=\frac{36.70\ g}{39.10\ g/mol}\approx0.9386$ mol.

Step1: Calculate moles of gold

First, use the formula $n=\frac{m}{M}$ to find the number of moles of gold. Given $m = 15.00$ g and $M = 197.0$ g/mol, so $n=\frac{15.00\ g}{197.0\ g/mol}\approx0.07614$ mol.

Step2: Use Avogadro's number

Avogadro's number $N_A=6.022\times 10^{23}$ atoms/mol. The number of atoms $N$ of gold is $N = n\times N_A$. Substitute $n = 0.07614$ mol and $N_A=6.022\times 10^{23}$ atoms/mol into the formula, we get $N=0.07614\ mol\times6.022\times 10^{23}$ atoms/mol $\approx4.585\times 10^{22}$ atoms.

Answer:

0.9386 mol