High School Chemistry : Acid-Base Chemistry

Study concepts, example questions & explanations for High School Chemistry

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Example Questions

Example Question #6 : Titrations

Which of the following aqueous solutions is the most concentrated?

Possible Answers:

All of these solutions have the same concentration.

Correct answer:

Explanation:

In order to answer this question, it helps to know that 1 kilogram of water is equal to 1 liter of water, due to its density. Two of the above options refer to a 1m solution of hydrochloric acid. The other is a 1M solution. 

All three of the options have the same amount of hydrochloric acid (one mole). For molarity, the hydrochloric acid is diluted with water until one liter of solution is created. For molality, one mole of HCl is added to one kilogram of water. Since one kilogram of water is one liter, this becomes the same concentration.

One a very small level, the 1M HCl solution will be slightly more concentrated. Creating a molal solution does not take into account the volume of the solute. If, for example, 100 cubic centimeters of HCl were added to one kilogram of water, the resulting volume would be more than one liter, making the concentration slightly less than 1M. This discrepancy is usually not accounted for in basic chemistry, but you should be familiar with the concept.

Example Question #1 : Concentration And Units

What is the molality of a solution created by mixing 4.3g NaCl into 43g of water?

Possible Answers:

Cannot be determined

Correct answer:

Explanation:

Molality can be defined:

Molality=\hspace{1 mm}\frac{mol\hspace{1 mm}solute}{kg\hspace{1 mm}solvent}

It is slightly different from Molarity and has different uses.

Molality=\hspace{1 mm}\frac{4.3\hspace{1 mm}g\hspace{1 mm}NaCl}{43\hspace{1 mm}g\hspace{1 mm}H_20}\times\frac{1000\hspace{1 mm}g\hspace{1 mm}H_2O}{1\hspace{1 mm}kg\hspace{1 mm}H_2O}\times\frac{1\hspace{1 mm}mole\hspace{1 mm}NaCl}{58.44\hspace{1 mm}g\hspace{1 mm}NaCl}=1.71\hspace{1 mm}m

 

Example Question #1 : Identifying Unknown Concentration

How much solid NaOH must be dissolved to make 740mL of a 0.32M solution?

Possible Answers:

9.47g

9.47 * 102g

The sodium hydroxide will boil off with the water

4.26g

12.8g

Correct answer:

9.47g

Explanation:

This problem can be solved by stoichiometry. Remember that 0.32M gives us the moles of NaOH per liter, and solve for the number of moles per 0.740L.

Example Question #9 : Titrations

Find the mass of  in 10L of water if it is a 2m solution.

Possible Answers:

Correct answer:

Explanation:

Molality is grams of solute per kilogram of solvent.

Water has a density of one gram per mililiter, so one liter of water equal to one kilogram. If we have a 2m solution, that means we have two moles of  per kilogram of water.

has a molecular weight of .

This gives us  of .

Example Question #10 : Titrations

10mL of a solution of  of unknown concentration mixed with 34mL of   produced a solution with a pH of 7. What is the concentration of the  solution?

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 molarity of the base:

Plug in known values and solve.

Example Question #11 : Identifying Unknown Concentration

30mL of a solution of  of unknown concentration mixed with 19mL of   produced a solution with a pH of 7. What is the concentration of the  solution?

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 molarity of the base:

Plug in known values and solve.

Example Question #72 : Acid Base Chemistry

29mL of a solution of   is mixed with 65mL of an  solution of unknown concentration produced a solution with a pH of 7. What is the concentration of the  solution?

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 molarity of the acid:

Plug in known values and solve.

Example Question #11 : Titrations

39mL of a solution of   is mixed with 24mL of an  solution of unknown concentration produced a solution with a pH of 7. What is the concentration of the  solution?

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 molarity of the acid:

Plug in known values and solve.

Example Question #11 : Titrations

It takes 25mL of a .001M  to neutralize 5mL of a solution of  of unknown concentration. What is the concentration of the unknown solution?
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 molarity of the acid:

Plug in known values and solve.

Example Question #71 : Acid Base Chemistry

It takes 35mL of .01M  to neutralize 5mL of a solution of  of unknown concentration. What is the concentration of the unknown solution?
Possible Answers:

None of these

Correct answer:

Explanation:

For this question use the following formula: 

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pastedGraphic_1.png is the number of acidic hydrogens on the acid, pastedGraphic_2.png is the molarity of the acid, pastedGraphic_3.png is the volume of the acid, pastedGraphic_4.png is the number of basic hydroxides on the base, pastedGraphic_5.png is the molarity of the base, pastedGraphic_6.png is the volume of the base

Rearrange the equation for the molarity of the acid:

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Plug in known values and solve.

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