The chemical formula for strontium sulfide is SrS. A chemist measured the amount of strontium sulfide produced during an experiment. She finds that 35.6 g of strontium sulfide is produced. Calculate the number of moles of strontium sulfide produced. Be sure your answer has the correct number of significant digits.
The correct answer and explanation is :
To calculate the number of moles of strontium sulfide (SrS) produced, we need to use the formula:
[
\text{moles} = \frac{\text{mass}}{\text{molar mass}}
]
Step 1: Calculate the molar mass of SrS
The molar mass of a compound is the sum of the atomic masses of the elements that make up the compound. From the periodic table:
- The atomic mass of strontium (Sr) is approximately 87.62 g/mol.
- The atomic mass of sulfur (S) is approximately 32.07 g/mol.
Therefore, the molar mass of SrS is:
[
\text{molar mass of SrS} = 87.62 \, \text{g/mol (Sr)} + 32.07 \, \text{g/mol (S)} = 119.69 \, \text{g/mol}
]
Step 2: Calculate the number of moles
We know the mass of strontium sulfide produced is 35.6 grams. Now, we can calculate the number of moles of SrS using the formula:
[
\text{moles} = \frac{35.6 \, \text{g}}{119.69 \, \text{g/mol}}
]
[
\text{moles} = 0.297 \, \text{mol}
]
Step 3: Significant Figures
The given mass, 35.6 grams, has 3 significant figures. Therefore, the number of moles must also be reported with 3 significant figures.
Final Answer:
The number of moles of strontium sulfide produced is:
[
\boxed{0.297 \, \text{mol}}
]
Explanation:
The process of calculating moles begins with finding the molar mass of the compound, which is essentially the mass of one mole of the substance. In this case, strontium sulfide (SrS) is made up of strontium (Sr) and sulfur (S), so we added the atomic masses of these two elements to get the molar mass of SrS. Once we had the molar mass, we divided the mass of the compound (35.6 g) by the molar mass (119.69 g/mol) to find the number of moles. The result was rounded to the appropriate number of significant digits to match the precision of the given data.