acid-base titration

Acid-Base Titration

Acid-Base Titration• Acid-base titration is a laboratory procedure used

to determine – among other things – the unknown concentration of an acid or a base.

Acid-Base Titration• During an acid-base titration, an acidic solution

of known concentration is added drop by drop to a base solution of unknown concentration (or vise versa) until all the hydrogen ions (H1+) have exactly neutralized all the hydroxide ions (OH1-).

OH1-

OH1-

OH1-

OH1-

OH1-

H1+

HOH

HOHHOH HOH

H1+HOHH1+HOH

H1+

HOHH1+

HOH

HOH...when moles H1+

equals moles OH1-.An appropriate

acid-baseindicator

will signal...

Acid-Base Titration• During an acid-base titration, an acidic solution

of known concentration is added drop by drop to a base solution of unknown concentration (or vise versa) until all the hydrogen ions (H1+) have exactly neutralized all the hydroxide ions (OH1-).

H1+

HOH

HOHHOH HOH

H1+HOHH1+HOH

H1+

HOHH1+

HOH

HOHHow many OH1-

ions were presentin the original

solution?

Count the number ofH1+ ions added.

H1+HOH

six

Acid-Base Titration• Remember, neutralization occurs when...

the moles of H1+ from the acid

=

the moles of OH1- from the base

• The point of exact neutralization is called the equivalence point and is signaled by a color change (end point) in an acid-base indicator.

Acid-Base Titration

1) How many moles of NaOH does it take to neutralize 1.5 mol HCl? ________

2) How many moles of LiOH does it take to neutralize 1.5 mol H2SO4? ________

3) How many moles of Ba(OH)2 does it take to neutralize 1.5 moles of HNO3? ________

4) How many moles of Ca(OH)2 does it take to neutralize 1.5 moles of H2CO3? ________

OHH 1.5 mol

OHH2 3.0 mol

(OH)2

H 0.75 mol

(OH)2

H2 1.5 mol

Acid-Base Titration• Once the titration is complete, the concentration of

the unknown solution is determined by employing the titration formula:

MAVA = MBVB

Beware:

• MA = molarity of H1+ but VA = volume of the acid!

• MB = molarity of OH1- but VB = volume of the base!

this equation is tricky!

MA H1+ VA acid

MB OH1- VB base

Acid-Base Titration• The molarity of H1+ is equal to the acid’s molarity

times the number of H1+’s on the acid.

MA = # H1+ x Macid

• The molarity of OH1- is equal to the base’s molarity times the number of OH1-’s on the base.

MB = # OH1- x Mbase

Acid-Base Titration

5) If the MA of an H2SO4 solution is 2.0 M, then what is molarity (M) of the H2SO4 solution?

MA = # H1+ x Macid

(x)(2)2.0 M =

x = 1.0 M H2SO4

1 H2SO4 canproduce 2 H1+!

M of H1+

Acid-Base Titration

6) If the molarity (M) of an HNO3 solution is 1.0 M, then what is the MA of the solution?

MA = # H1+ x Macid

1 HNO3 can

produce 1 H1+!x = (1.0 M)(1)

x = 1.0 M H1+

M of H1+

Acid-Base Titration

7) If the MA of an H3PO4 solution is 1.2 M, then what is molarity (M) of the H3PO4 solution?

MA = # H1+ x Macid

1 H3PO4 canproduce 3 H1+!

(x)(3)1.2 M =

0.40 M H3PO4x =

M of H1+

Acid-Base Titration

8) If the molarity (M) of an Ba(OH)2 solution is 0.25 M, then what is the MB of the

solution?

MB = # OH1- x Mbase 1 Ba(OH)2 canproduce 2 OH1-!

(0.25 M)(2)x =

x = 0.50 M OH1-

M of OH1-

Acid-Base Titration

9) If the MB of an Ca(OH)2 solution is 1.0 M, then what is molarity (M) of the Ca(OH)2 solution?

MB = # OH1- x Mbase

1 Ca(OH)2 canproduce 2 OH1-!

(x)(2)1.0 M =

0.50 M Ca(OH)2x =

M of OH1-

Acid-Base Titration

10) If the molarity (M) of an NaOH solution is 0.12 M, then what is the MB of the

solution?

MB = # OH1- x Mbase1 NaOH can

produce 1 OH1-!(0.12 M)(1)x =

0.12 M OH1-x =

M of OH1-

Acid-Base Titration

11) How many milliliters of a 1.50 M solution of H2SO4 would exactly neutralize 7.50 mL of a 0.250 M solution of Ba(OH)2?

MAVA = MBVB

Choose an appropriate acid-base indicator.

__________________methyl orange orbromcresol green

(7.50 mL)(0.500 M)(x) =(3.00 M)

1.25 mLx =

Acid-Base Titration

12) If 20.0 mL of an unknown solution of HCl is titrated with a 2.0 M solution of NaOH such that it required 37.0 mL of the NaOH to

reach the end point, what is the molarity of the HCl?

MAVA = MBVB


__________________

(37.0 mL)(2.0 M)(20.0 mL) =(x)

3.7 Mx =

litmus or bromthymol blue

of H1+

The molarity of the HCl = 3.7 M

Acid-Base Titration

13) If 150.0 mL of 0.050 M H2CrO4 solution is titrated against a 0.30 M NaOH solution,

then how many milliliters of the base would be needed to reach the end point?

MAVA = MBVB


__________________thymol blue or

phenolphthalein

(x)(0.30M)(150.0 mL) =(0.100 M)

50. mLx =

Acid-Base Titration

14) What is the molar concentration of a 25.0 mL sample of NH3 (NH4OH) if it takes 8.0 mL of a 0.15 M solution of HBr to neutralize the NH3

(NH4OH)?

MAVA = MBVB



(25.0 mL)(x)(8.0 mL) =(0.15 M)

0.048 M x = of OH1-

The molarity of the NH3 = 0.048 M

Acid-Base Titration

15) How many milliliters of 0.10 M nitric acid (HNO3) would be needed to neutralize 16.0 mL of a 0.15 M solution of Ba(OH)2?

MAVA = MBVB



(16.0 mL)(0.30 M)(x) =(0.10 M)

48 mLx =

Acid-Base Titration

16) A student neutralized 16.4 milliliters of HCl by adding 12.7 milliliters of 0.620 M KOH.What was the molarity of the HCl acid?

MAVA = MBVB


__________________litmus or

bromthymol blue

(12.7 mL)(0.620 M)(16.4 mL) =(x)

0.480 Mx = of H1+

The molarity of the HCl = 0.480 M

17) What is the molarity of a solution containing 20.0 grams of NaOH in 500. milliliters of solution?

x = __________ x = __________

Acid-Base Titration

20.0 g40.0 g/mol

0.500 mol0.500 L

M = mol L

# mol = given massGFM

1.00 M x =x = 0.500 mol

acid-base titration

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