Question

11,9g of potassium bromide dissolved in 3dm³ of solution

Answer 1

To find the concentration of potassium bromide (KBr) in the solution, you need to follow these steps:

1. **Calculate the number of moles of KBr**:
- First, find the molar mass of KBr:
- Potassium (K) has an atomic mass of approximately 39.1 g/mol.
- Bromine (Br) has an atomic mass of approximately 79.9 g/mol.
- Therefore, the molar mass of KBr = 39.1 g/mol + 79.9 g/mol = 119.0 g/mol.

- Now calculate the number of moles of KBr in 11.9 g:
\[
\text{Moles of KBr} = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{11.9 \, \text{g}}{119.0 \, \text{g/mol}} \approx 0.100 \, \text{mol}
\]

2. **Calculate the concentration in mol/dm³ (Molarity)**:
- To find the concentration (C) in moles per cubic decimeter (mol/dm³), use the formula:
\[
C = \frac{\text{Moles of solute}}{\text{Volume of solution in dm}^3}
\]
- Here the volume of the solution is given as 3 dm³:
\[
C = \frac{0.100 \, \text{mol}}{3 \, \text{dm}^3} \approx 0.0333 \, \text{mol/dm}^3
\]

Thus, the concentration of the potassium bromide solution is approximately **0.0333 mol/dm³**.