Practice Questions
Concept Explanation
Concentration measures the amount of solute in a solution. When mixing solutions, the total amount of solute is conserved while volume changes.
Key Formulas
- Concentration = (amount of solute / total volume) × 100%
- When mixing: C1V1 + C2V2 = Cm(V1 + V2)
- Amount of solute = (concentration/100) × volume
Example
Mix 200 ml of 10% acid with 300 ml of 20% acid. Solute = 20 + 60 = 80 ml in 500 ml = 16%.
Common Trap
Add solute amounts directly, not concentrations. Always divide by total volume for the final concentration.
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Q1 Easy
200 ml of 10% acid and 300 ml of 20% acid. Final concentration is:
ExplanationSolute = 20 + 60 = 80 ml in 500 ml = 16%. -
Q2 Medium
500 ml of 20% solution and 300 ml of 30% solution. Final concentration is:
ExplanationSolute = 100 + 90 = 190 in 800 ml = 23.75%. -
Q3 Easy
100 ml of 40% salt solution contains salt:
ExplanationSalt = 0.4 × 100 = 40 ml. -
Q4 Medium
60 ml of 25% alcohol and 40 ml of 15% alcohol. Final concentration is:
ExplanationSolute = 15 + 6 = 21 in 100 ml = 21%. -
Q5 Medium
300 ml of 8% solution and 200 ml of 18% solution. Final concentration is:
ExplanationSolute = 24 + 36 = 60 in 500 ml = 12%. -
Q6 Hard
How much 30% acid to mix with 100 ml of 10% acid for 20% acid?
Explanation10 + 0.3x = 0.2(100 + x) gives 0.1x = 10, x = 100 ml. -
Q7 Medium
150 ml of 12% and 250 ml of 8%. Final concentration is:
ExplanationSolute = 18 + 20 = 38 in 400 ml = 9.5%.
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Q8 Easy
400 ml of 5% sugar and 600 ml of 15% sugar. Final concentration is:
ExplanationSolute = 20 + 90 = 110 in 1000 ml = 11%. -
Q9 Hard
80 ml of 50% and 20 ml of 10%. Final concentration is:
ExplanationSolute = 40 + 2 = 42 in 100 ml = 42%. -
Q10 Easy
250 ml of 16% and 250 ml of 24%. Final concentration is:
ExplanationEqual volumes: mean = (16 + 24)/2 = 20%. -
Q11 Medium
120 ml of 35% and 80 ml of 5%. Final concentration is:
ExplanationSolute = 42 + 4 = 46 in 200 ml = 23%. -
Q12 Easy
Solute in 75 ml of 28% solution is:
ExplanationSolute = 0.28 × 75 = 21 ml. -
Q13 Hard
Which mix gives 15% concentration?
ExplanationOption C: (12 + 33)/300 = 15%. -
Q14 Hard
100 ml of 20% solution. Water added to make 10%. Final volume is:
ExplanationSolute = 20 ml. 20/V = 0.1, V = 200 ml.
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DS1 Easy
What is the final concentration?
Statement I200 ml of 10% acid and 300 ml of 20% acid are mixed.
Statement IITotal solute is 80 ml in 500 ml.
ExplanationEach gives 80/500 = 16%. -
DS2 Easy
How much solute is in the solution?
Statement IVolume is 100 ml at 40% concentration.
Statement II40 ml of solute is present.
ExplanationEach gives 40 ml of solute.
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DS3 Medium
Is final concentration above 20%?
Statement I500 ml of 20% and 300 ml of 30% are mixed.
Statement II150 ml of 12% and 250 ml of 8% are mixed.
ExplanationI gives 23.75% > 20%. II gives 9.5%. -
DS4 Hard
What volume of 30% solution is needed?
Statement I100 ml of 10% acid is available.
Statement IIFinal concentration must be 20%.
ExplanationNeed both: 100 ml of 30% acid.