MCAT Physical : Solubility and Ions

Study concepts, example questions & explanations for MCAT Physical

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Example Questions

Example Question #1229 : Mcat Physical Sciences

A chemist has 300mL of a 0.75M solution and needs to dilute it to 0.35M. How much solvent should be added?

Possible Answers:

Correct answer:

Explanation:

Use the equation for molarity, , first to figure out the number of moles of solute present.

 \frac{moles}{0.300 liters} = 0.75 M

Solving this gives 0.225 moles of solute. Using the same equation again with the final molarity will give the final volume.

Finally, the amount of solvent added is the difference between initial and final total volumes.

0.643L – 0.300L = 0.342L added

Example Question #5 : Concentration, Dilution, And Units

If 0.02L of a 0.7N NaCl solution is diluted to 1L, what is the new concentration?

Possible Answers:

Correct answer:

Explanation:

In this particular scenario, molarity can be used interchangeably with normality. The product of the initial normality and initial volume will be equal to the product of the final normality and final volume.

Our initial normality is 0.7N and our initial volume is 0.02L. We also know our final volume is 1L.

Solve for the final concentration.

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