Let's solve each problem step by step.
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Problem 1:
What is the concentration of 75 ml of ethanol mixed with 500 ml of water?
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Given:
- Amount of Solute = 75 mL (ethanol)
- Amount of Solution = 75 mL (ethanol) + 500 mL (water) = 575 mL
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Formula:
\[ \text{Concentration} = \frac{\text{Amount of Solute}}{\text{Amount of Solution}} \]
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Solution:
\[ \text{Concentration} = \frac{75 \, \text{mL}}{575 \, \text{mL}} \]
Convert to a percentage:
\[ \text{Concentration} = \left( \frac{75}{575} \right) \times 100\% \]
\[ \text{Concentration} = 0.1304 \times 100\% \]
\[ \text{Concentration} = 13.04\% \]
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Answer:
\[ \boxed{13.04\%} \]
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Problem 2:
If the concentration of the solution is 2% and the volume of the solution is 250 mL, what is the volume of solute in this solution?
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Given:
- Concentration = 2%
- Amount of Solution = 250 mL
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Formula:
\[ \text{Amount of Solute} = \text{Amount of Solution} \times \text{Concentration} \]
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Solution:
\[ \text{Amount of Solute} = 250 \, \text{mL} \times 2\% \]
\[ \text{Amount of Solute} = 250 \, \text{mL} \times 0.02 \]
\[ \text{Amount of Solute} = 5 \, \text{mL} \]
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Answer:
\[ \boxed{5 \, \text{mL}} \]
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Problem 3:
If I make a solution by adding water to 35 mL of methanol until the final volume of the solution is 275 mL, what is the concentration of methanol in this solution?
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Given:
- Amount of Solute = 35 mL (methanol)
- Amount of Solution = 275 mL
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Formula:
\[ \text{Concentration} = \frac{\text{Amount of Solute}}{\text{Amount of Solution}} \]
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Solution:
\[ \text{Concentration} = \frac{35 \, \text{mL}}{275 \, \text{mL}} \]
Convert to a percentage:
\[ \text{Concentration} = \left( \frac{35}{275} \right) \times 100\% \]
\[ \text{Concentration} = 0.1273 \times 100\% \]
\[ \text{Concentration} = 12.73\% \]
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Answer:
\[ \boxed{12.73\%} \]
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Final Answers:
1. \( \boxed{13.04\%} \)
2. \( \boxed{5 \, \text{mL}} \)
3. \( \boxed{12.73\%} \)
Parent Tip: Review the logic above to help your child master the concept of concentration worksheet.
