Question

1. how many moles are in 15 grams of lithium?
2. how many grams are in 2.4 moles of sulfur?
3. how many moles are in 22 grams of argon?
4. how many grams are in 88.1 moles of magnesium?
5. how many moles are in 2.3 grams of phosphorus?
6. how many grams are in 11.9 moles of chromium?
7. how many moles are in 9.8 grams of calcium?
8. how many grams are in 238 moles of arsenic?

Explanation:

Step1: Recall the formula for moles

The formula for moles \(n=\frac{m}{M}\), where \(m\) is the mass in grams and \(M\) is the molar mass in \(g/mol\). For grams \(m = n\times M\). Look up the molar masses: \(M_{Li}=6.94\ g/mol\), \(M_{S}=32.07\ g/mol\), \(M_{Ar}=39.95\ g/mol\), \(M_{Mg}=24.31\ g/mol\), \(M_{P}=30.97\ g/mol\), \(M_{Cr}=52.00\ g/mol\), \(M_{Ca}=40.08\ g/mol\), \(M_{As}=74.92\ g/mol\)

Step2: Calculate for each question

1) For lithium

\(n=\frac{m}{M}=\frac{15\ g}{6.94\ g/mol}\approx2.16\ mol\)

2) For sulfur

\(m = n\times M=2.4\ mol\times32.07\ g/mol = 76.97\ g\)

3) For argon

\(n=\frac{m}{M}=\frac{22\ g}{39.95\ g/mol}\approx0.55\ mol\)

4) For magnesium

\(m = n\times M=88.1\ mol\times24.31\ g/mol=2141.71\ g\)

5) For phosphorus

\(n=\frac{m}{M}=\frac{2.3\ g}{30.97\ g/mol}\approx0.07\ mol\)

6) For chromium

\(m = n\times M=11.9\ mol\times52.00\ g/mol = 618.8\ g\)

7) For calcium

\(n=\frac{m}{M}=\frac{9.8\ g}{40.08\ g/mol}\approx0.24\ mol\)

8) For arsenic

\(m = n\times M=238\ mol\times74.92\ g/mol=17830.96\ g\)

Answer:

1. Approximately \(2.16\) moles.
2. Approximately \(76.97\) grams.
3. Approximately \(0.55\) moles.
4. Approximately \(2141.71\) grams.
5. Approximately \(0.07\) moles.
6. Approximately \(618.8\) grams.
7. Approximately \(0.24\) moles.
8. Approximately \(17830.96\) grams.