how to find volume chemistry

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

Correct answer:

25mL

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.

$H_2SO_4\rightleftharpoons 2H^++SO_4^{2-}$

$KOH\rightleftharpoons K^++OH^-$

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).

$H_2SO_4+2KOH\rightleftharpoons 2H_2O+K_2SO_4$

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

$M=\frac{mol}{L}\rightarrow mol=(M)(L)$

$mol=(0.5M)(50mL)=(0.5M)(0.05L)=0.025mol\ KOH$

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

$0.025mol\ KOH*\frac{1mol\ H_2SO_4}{2mol\ KOH}*\frac{1L}{0.5mol\ H_2SO_4}=0.025L\ H_2SO_4$

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

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?

Correct answer:

$\small 12.5mL$

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.

$\small M_{1}v_{1} = M_{2}v_{2}$

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

$\small (2M)v_{1} = (0.5M)(50 mL)$

$\small v_{1} = \frac{(0.5M)(50mL)}{2M}=12.5 mL$

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.

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

Correct answer:

15mL

Explanation:

For this question use the following formula:

N_A M_A V_A = N_B M_B V_B

N_A 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:

$\frac{N_A M_A V_A }{N_B M_B}= V_B$

Plug in known values and solve.

V_B=15mL

Starting with 50mL of a .015M HNO_3 solution, how many milliliters of .010M NaOH solution are needed to titrate it?

Correct answer:

75mL

Explanation:

For this question use the following formula:

N_A M_A V_A = N_B M_B V_B

Rearrange the equation for the volume of the base:

$\frac{N_A M_A V_A }{N_B M_B}= V_B$

Plug in known values and solve.

V_B=75mL

Starting with 25mL of a .001M HNO_3 solution, how many milliliters of .010M Mg(OH)_2 solution are needed to titrate it?

Correct answer:

1.25mL

Explanation:

For this question use the following formula:

N_A M_A V_A = N_B M_B V_B

Rearrange the equation for the volume of the base:

$\frac{N_A M_A V_A }{N_B M_B}= V_B$

Plug in known values and solve.

V_B=1.25mL

Starting with 75mL of a .030M HNO_3 solution, how many milliliters of .022M NaOH solution are needed to titrate it?

Correct answer:

102mL

Explanation:

For this question use the following formula:

N_A M_A V_A = N_B M_B V_B

Rearrange the equation for the volume of the base:

$\frac{N_A M_A V_A }{N_B M_B}= V_B$

Plug in known values and solve.

V_B=102mL

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

Correct answer:

540mL

Explanation:

For this question use the following formula:

N_A M_A V_A = N_B M_B V_B

Rearrange the equation for the volume of the base:

$\frac{N_A M_A V_A }{N_B M_B}= V_B$

Plug in known values and solve.

V_B=540mL

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

Correct answer:

75mL

Explanation:

For this question use the following formula:

N_A M_A V_A = N_B M_B V_B

Rearrange the equation for the volume of the base:

$\frac{N_A M_A V_A }{N_B M_B}= V_B$

Plug in known values and solve.

V_B=75mL

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