To find the concentration of potassium bromide (KBr) in the solution, you need to follow these steps:
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Calculate the number of moles of KBr:
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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.
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Now calculate the number of moles of KBr in 11.9 g: \[ \text{Moles of KBr} = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{11.9 , \text{g}}{119.0 , \text{g/mol}} \approx 0.100 , \text{mol} \]
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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.