Chemical Calculation: How Many Grams of KBr are Dissolved in Solution?

How many grams of KBr are dissolved in 72.7 mL of a 0.998 M solution?

8.63 grams of KBr are dissolved in 72.7 mL of a 0.998 M solution. What is the calculation behind this?

Answer:

The calculation to determine the number of grams of KBr dissolved in a 0.998 M solution in 72.7 mL involves understanding molarity and molar mass.

First, we need to calculate the molar mass of KBr. By looking at the molar weights of potassium (K) and bromine (Br) on the periodic table, we find that:

Molar mass of K: 39.098 g/mol

Molar mass of Br: 79.904 g/mol

Therefore, the molar mass of KBr is:

39.098 g/mol + 79.904 g/mol = 119 g/mol

Next, we know that the solution is 0.998 M, meaning that there are 0.998 moles of KBr in 1000 mL of the solution. To calculate the number of moles in 72.7 mL, we use the formula:

Number of moles of KBr = 72.7 mL × 0.998 mol/L / 1000 mL/L = 0.0725 moles

Using the molar mass, we can then calculate the mass in grams in the sample:

Mass of KBr = 0.0725 moles * 119 g/mol = 8.6275 g ≈ 8.63 g

This explains how 8.63 grams of KBr are dissolved in 72.7 mL of a 0.998 M solution.