The chemical formula for potassium bromide is KBr. A chemist measured the amount of potassium bromide produced during an experiment. She finds that 58.1 g of potassium bromide is produced. Calculate the number of moles of potassium bromide 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 potassium bromide (KBr) produced, we use the formula:
[
\text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}}
]
Step 1: Identify the mass
The mass of potassium bromide produced is given as 58.1 grams.
Step 2: Determine the molar mass of KBr
Potassium bromide (KBr) consists of two elements: potassium (K) and bromine (Br). To find the molar mass of KBr, we need to sum the atomic masses of these two elements:
- Atomic mass of potassium (K) = 39.1 g/mol
- Atomic mass of bromine (Br) = 79.9 g/mol
The molar mass of KBr is:
[
\text{Molar Mass of KBr} = 39.1 \, \text{g/mol} + 79.9 \, \text{g/mol} = 119.0 \, \text{g/mol}
]
Step 3: Calculate the number of moles
Now we can use the formula to calculate the number of moles of potassium bromide produced:
[
\text{Moles of KBr} = \frac{58.1 \, \text{g}}{119.0 \, \text{g/mol}} = 0.488 \, \text{mol}
]
Step 4: Consider significant digits
The mass of KBr is provided to three significant digits (58.1 g), and the molar mass of KBr has three significant digits (119.0 g/mol). Therefore, the final answer should be reported with three significant digits.
Thus, the number of moles of potassium bromide produced is:
[
0.488 \, \text{mol}
]
Explanation:
The process involves converting the mass of a substance into the number of moles, which is a direct measure of the amount of a substance in terms of its molecular quantity. The conversion relies on the molar mass, a constant derived from the sum of the atomic masses of the constituent elements. The number of moles is crucial in stoichiometric calculations because it relates the mass of a substance to the number of molecules or atoms it contains.