A 20.0 mL sample of a 15.5% (m/v) KBr solution is taken. What mass of KBr (in grams) is present in this sample?

• A. 7.75 g
• B. 0.31 g
• C. 3.10 g
• D. 1.55 g

Answer: (C)

Verified step by step guidance

1. Understand that a 15.5% (m/v) KBr solution means there are 15.5 grams of KBr dissolved in 100 mL of solution.
2. Write the relationship for mass of KBr in the given volume using the percentage concentration: \(\text{mass of KBr} = \left( \frac{15.5 \, \text{g}}{100 \, \text{mL}} \right) \times \text{volume of solution in mL}\).
3. Substitute the given volume of 20.0 mL into the equation: \(\text{mass of KBr} = \left( \frac{15.5}{100} \right) \times 20.0\).
4. Perform the multiplication to find the mass of KBr in grams (do not calculate the final number here, just set up the expression).
5. Interpret the result as the mass of KBr present in the 20.0 mL sample of the solution.