Question

the problems below will be worth 2 mastery points each. 1 point each for correct work, and 1 for the correct answer. round your answers to 3 significant figures and include units.

1. convert 3.72 x 10²² molecules of h₂o to moles.
2. convert 3.75 moles of iron to atoms of iron.

Explanation:

Step1: Recall Avogadro's number

Avogadro's number, \(N_A = 6.022\times 10^{23}\text{ molecules/mol}\)

Step2: Use the formula \(n=\frac{N}{N_A}\)

For \(N = 3.72\times 10^{22}\text{ molecules}\) of \(H_2O\), \(n=\frac{3.72\times 10^{22}}{6.022\times 10^{23}}\)

$$n=\frac{3.72}{6.022}\times10^{- 1}$$

$$n = 0.0618\text{ mol}$$

Step3: Recall Avogadro's number for the second problem

Avogadro's number \(N_A=6.022\times 10^{23}\text{ atoms/mol}\)

Step4: Use the formula \(N=n\times N_A\)

For \(n = 3.75\text{ mol}\) of \(Fe\), \(N=3.75\times6.022\times 10^{23}\)

$$N=(3.75\times6.022)\times 10^{23}$$

$$N = 2.26\times 10^{24}\text{ atoms}$$

Answer:

1. \(0.0618\text{ mol}\)
2. \(2.26\times 10^{24}\text{ atoms}\)