A solution has a molality of 0.959 mol/kg for KBr and contains 0.350 kg of solvent. What mass of KBr (in grams) is present in the solution?

• A. 28.0 g
• B. 40.1 g
• C. 56.2 g
• D. 18.7 g

Answer: (B)

Verified step by step guidance

1. Identify the given information: molality (m) = 0.959 mol/kg and mass of solvent = 0.350 kg.
2. Recall the definition of molality: molality (m) = moles of solute / mass of solvent (in kg). Rearranged, moles of solute = molality \times mass of solvent.
3. Calculate the moles of KBr by multiplying the molality by the mass of the solvent: moles of KBr = 0.959 mol/kg \times 0.350 kg.
4. Find the molar mass of KBr by adding the atomic masses of potassium (K) and bromine (Br). Use the periodic table values: approximately 39.1 g/mol for K and 79.9 g/mol for Br.
5. Calculate the mass of KBr by multiplying the moles of KBr by its molar mass: mass of KBr (g) = moles of KBr \times molar mass of KBr.