High School Chemistry : Identifying Unknown Volume

Study concepts, example questions & explanations for High School Chemistry

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Example Questions

Example Question #1 : Identifying Unknown Volume

What volume of 0.5M sulfuric acid is needed to neutralize 50mL of 0.5M potassium hydroxide? 

Possible Answers:

Correct answer:

Explanation:

Sulfuic acid is a diprotic acid and will give two hydrogen ions for each molecule of sulfuric acid that is completely dissociated. Potassium hydroxide has only one hyroxide ion per molecule.

Both of these compounds are strong, meaning they will dissociate completely in solution (potassium hydroxide is a strong base and sulfuric acid is a strong acid).

First, we need to find the moles of potassium hydroxide from the given volume and molarity.

Use stoichiometry to find the volume of sulfuric acid needed to react 0.1mol of potassium hydroxide.

Our final volume of sulfuric acid is 0.025L, or 25mL.

 

Example Question #2 : Identifying Unknown Volume

A chemist has a bottle containing a 2M aqueous solution of hydrochloric acid. He needs to create a 50mL solution of hydrochloric acid that has a concentration of 0.5M. What is the volume of 2M hydrochloric acid that he should dilute in order to achieve the desired concentration?

Possible Answers:

Correct answer:

Explanation:

In order to dilute the concentrated acid, we need to find the amount of concentrated acid that will be diluted to 50mL of total solution. We can find the volume of concentrated acid necessary by setting the final volume and concentration equal to the initial concentration and unknown volume.

The initial concentration is 2M, the final concentration is 0.5M, and the final volume is 50mL

This means that 12.5mL of concentrated acid needs to be diluted to 50mL of solution. This will result in a solution with a concentration of 0.5M.

Example Question #3 : Identifying Unknown Volume

Starting with 30mL of a .005M  solution, how many milliliters of .010M  solution are needed to titrate it?

Possible Answers:

None of these

Correct answer:

Explanation:

For this question use the following formula: 

 is the number of acidic hydrogens on the acid,  is the molarity of the acid,  is the volume of the acid,  is the number of basic hydroxides on the base,  is the molarity of the base,  is the volume of the base

Rearrange the equation for the volume of the base:

 

Plug in known values and solve.

Example Question #4 : Identifying Unknown Volume

Starting with 50mL of a .015M  solution, how many milliliters of .010M  solution are needed to titrate it?

Possible Answers:

None of these

Correct answer:

Explanation:

For this question use the following formula: 

 is the number of acidic hydrogens on the acid,  is the molarity of the acid,  is the volume of the acid,  is the number of basic hydroxides on the base,  is the molarity of the base,  is the volume of the base

Rearrange the equation for the volume of the base:

 

Plug in known values and solve.

Example Question #5 : Identifying Unknown Volume

Starting with 25mL of a .001M  solution, how many milliliters of .010M  solution are needed to titrate it?

Possible Answers:

None of these

Correct answer:

Explanation:

For this question use the following formula: 

 is the number of acidic hydrogens on the acid,  is the molarity of the acid,  is the volume of the acid,  is the number of basic hydroxides on the base,  is the molarity of the base,  is the volume of the base

Rearrange the equation for the volume of the base:

 

Plug in known values and solve.

Example Question #6 : Identifying Unknown Volume

Starting with 75mL of a .030M  solution, how many milliliters of .022M  solution are needed to titrate it?

Possible Answers:

None of these

Correct answer:

Explanation:

For this question use the following formula: 

 is the number of acidic hydrogens on the acid,  is the molarity of the acid,  is the volume of the acid,  is the number of basic hydroxides on the base,  is the molarity of the base,  is the volume of the base

Rearrange the equation for the volume of the base:

 

Plug in known values and solve.

Example Question #7 : Identifying Unknown Volume

Starting with 12mL of a .015M  solution, how many milliliters of .000M  solution are needed to titrate it?

Possible Answers:

None of these

Correct answer:

Explanation:

For this question use the following formula: 

 is the number of acidic hydrogens on the acid,  is the molarity of the acid,  is the volume of the acid,  is the number of basic hydroxides on the base,  is the molarity of the base,  is the volume of the base

Rearrange the equation for the volume of the base:

 

Plug in known values and solve.

Example Question #8 : Identifying Unknown Volume

Starting with 50mL of a .015M  solution, how many milliliters of .010M  solution are needed to titrate it?

Possible Answers:

None of these

Correct answer:

Explanation:

For this question use the following formula: 

 is the number of acidic hydrogens on the acid,  is the molarity of the acid,  is the volume of the acid,  is the number of basic hydroxides on the base,  is the molarity of the base,  is the volume of the base

Rearrange the equation for the volume of the base:

 

Plug in known values and solve.

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