Practice 2

Question 1

Which of the following statements about titrations is NOT correct?

AThe equivalence point is obtained by adding the stoichiometric amount of titrant to the analyte
solution.
b. The endpoint is marked by a sudden change in some physical property (e.g., color) of the
solution.
c. The difference between (1) and (2) above is the titration error.
d. None of the given options.
e. A blank titration involves carrying out the normal titration procedure, but without the analyt

Answer 1

None of the given options

Question 2

EDTA always react with metal ions in a __________ metal-EDTA complex.

Answer 2

1:1

Question 3

Total hardness in water is due to _____________.

Answer 3

calcium and magnesium

Question 4

The free EBT indicator is __________ in color at pH 10.

Answer 4

blue

Question 5

The pH meter is based on the principle of

Answer 5

potentiometer

Question 6

What is the effect on the following on the reported concentration of an HCl solution which was determined by titration with standard NaOH?

An air bubble was present inside the nozzle of the buret containing the base and remained there throughout the titration.

Answer 6

Increase

Question 7

What is the effect on the following on the reported concentration of an HCl solution which was determined by titration with standard NaOH?

At the end point, with phenolphthalein indicator, the color of the solution was dark pink.

Answer 7

Increase

Question 8

What is the effect on the following on the reported concentration of an HCl solution which was determined by titration with standard NaOH?

Some of the acid in the flask spilled out during titration.

Answer 8

Decrease

Question 9

What is the effect on the following on the reported concentration of an HCl solution which was determined by titration with standard NaOH?

The HCl solution was measured into a wet flask prior to titration.

Answer 9

No effect

Question 10

The second endpoint in carbonate titration is sharpened by

Boiling off excess water
b. Using methyl orange indicator
c. Boiling off carbon dioxide formed
d. All of the choices
e. None of the choices

Answer 10

Boiling off carbon dioxide formed

Question 11

One of these errors may have been incurred even if the precision of the results of the analysis is high.

Answer 11

Use of impure reagents for the preparation of standard solution

Question 12

Correct procedure for a titration include which of the following?

I. Draining the pipet by touching the tip to the side of the container used for the titration.
II. Rinsing the buret with distilled water before filling it with liquid to be used in titration.
III. Swirling the solution frequently during the titration.

Answer 12

I and III

Question 13

To determine the molar mass of a solid monoprotic acid, a student titrated a weight sample of the acid with standard NaOH. Which of the following could lead to a larger molar mass?

I. Failure to rinse all the acid from the weighing container into the beaker.
II. Addition of more water than was needed to dissolve the acid.
III. Addition of some base beyond equivalence point

Answer 13

I Failure to rinse all the acid from the weighing container into the beaker.

Question 14

An acid-base titration is not feasible of

Question 15

In the titration of a weak acid with a strong base, at the equivalence point

Question 16

Which of the following is not a primary standard for HCl?

Question 17

Which of the following is a primary standard for NaOH?

Question 18

Which of the following indicators can be used in a weak base-strong acid titration?

Question 19

Which of the following can be used for strong acid-base titrations?

Question 20

The following acids can be used as standard solution in acid-based titration EXCEPT

Question 21

A sample contained a mixture of NaHCO3, NaCO3 and inert material. If A represents the millilitres of standard acid to reach the phenolphthalein end point and B the volume of acid needed to go from this point to the methyl orange end point, which of the following relationships will be observed?

Question 22

At the equivalence point in the titration of a weak acid, HA, with strong base, KOH, all of the following statements are true EXCEPT

Question 23

A high equivalent weight is desirable for compounds used as primary standards because

Question 24

10 millimole of a monoprotic acid, HA, are titrated with a base, MOH. The following combinations are possible: A) strong acid vs strong base B) strong acid vs weak base C) weak acid vs strong base. At the equivalence point the pH is 7.

Question 25

At the equivalence point only the aqueous solution of the salt formed from the acid and base exists.

Question 26

Phenolphthalein indicator may be used to indicate the endpoint.

Question 27

A chemist received different mixtures for analysis with the statement that they contained NaOH, NaHCO3, Na2CO3 or compatible mixtures of these substances together with inert material. From the data given, identify the respective materials. Sample 1. With phenolphthalein as indicator, 24.32 mL was used. A duplicate sample required 48.64 with methyl orange as indicator.

Question 28

Sample 2. The addition of phenolphthalein caused no color change. With methyl orange, 38.47 mL of the acid required.

Question 29

Sample 3. To cause a color change with phenolphthalein in the cold, 15.29 mL of the acid was necessary, and an additional 33.19 mL was required for complete neutralization.

Question 30

Sample 4. The sample was titrated with acid until the pink of phenolphthalein disappeared; this process required 39.96 mL. On adding an excess of the acid, boiling and titrating back with NaOH, it was found that the base was equivalent to the excess acid.

Question 31

Which of the following is a primary standard for EDTA?

Question 32

Which of the following statements is true?

Question 33

Which of the following is not a desirable property of an indicator to be used in a complexometric titration that involves EDTA?

Question 34

In the double indicator titration of a sample containing 3:1 ratio of millimoles Na2CO3 to millimoles NaHCO3 with 0.100 M HCl, the relationship between Va (volume to phenolphthalein end point) and Vb (volume from phenolphthalein to methyl orange endpoint)

Question 35

The total alkalinity of broiler feed water often is determined by titrating the various metal bicarbonates with a standard acid. Calculate the total alkalinity as mg CaCO3 in/ 100 mL water in a 50.00 mL water sample that requires 37.92 mL of 0.08672 M HCl for titration to the methyl orange end point.

Question 36

For which of the following titrations can either methyl orange or phenolphthalein indicator to be used?

Question 37

A sample of KHP (204.22 g/mol) weighing 589.3 mg was titrated with NaOH requiring 22.49 mL to reach the end point. Calculate the molar concentration of the NaOH solution.

Question 38

Calculate the volume of 0.2305 M HCl necessary to react with 26.35 mL of 0.2005 M Na2CO3.

Question 39

Calculate the volume of 0.2305 M HCl necessary to react with 325.69 mg of 99.95% HgO (216.59).

Question 40

Calculate the volume of 0.2305 M HCl necessary to react with 158.27 mg of THAM (121.14).

Question 41

A 5.00 mL aliquot of wine vinegar was titrated with 0.1104 M NaOH requiring 32.88 mL to reach phenolphthalein end point. If vinegar has a density of 1.055 g/mL, calculate % acetic acid in the vinegar sample.

Question 42

A chemist wants to prepare a standard solution containing 300 micrograms per mL Ca. What weight of standard calcium carbonate (CaCO3, 98.5% pure) should be dissolved in a minimum volume of 6.0 M HCl and subsequently diluted to 1.00 L?

Question 43

A sample of impure calcite (CaCO3, 100.1), which weighs 0.4950 g is dissolved in 50 mL of 0.1000 N acid and the excess acid is titrated with 5.25 mL of standard base (1.050 mL acid = 1.000 mL base). Calculate the % CaCO3 in the sample.

Question 44

A 100-mL sample of drinking water was buffered at pH 10.0 and after the addition of Calmagite indicator required 38.41 mL of 4.652 x 10^-3 M EDTA for titration. Calculate the total hardness of water in ppm CaO (56.08).

Question 45

An EDTA solution was prepared by dissolving the disodium salt in 1 L of water. It was standardized using 0.5063 gram of primary standard calcium carbonate and consumed 28.50 mL of the solution. The standard solution was used to determine the hardness of a 2 L sample of mineral water, which required 35.57 mL of EDTA solution. Express the analysis in terms of ppm CaCO3.

Question 46

A 1.00 mL aliquot of fish oil was analysed for nitrogen using the Kjeldahl method. After digestion, the distilled ammonia was collected in a 100 mL of 0.0503 M HCl. The excess HCl required 28.3 mL of 0.124 M NaOH for titration. Calculate the amount of nitrogen in mg/mL.

Question 47

To extract Al from glass, 100 mL EDTA were mixed with 0.50 g of glass particles and allowed to equilibrate over time. The Al concentration of the solution was found to be 5.25 micromolar. If the glass contained 0.80 wt% Al, what percent of the Al was extracted by the EDTA?

Question 48

A 50.0 mL solution containing Zn2+ was treated with 25 mL of 0.0452 M EDTA. The excess EDTA needed 29.2 mL 0.0123 M Mg2+ to reach the equivalence point. What was the molarity of Zn2+ solution?

Question 49

The protein content of a sample was determined by a Kjeldahl analysis for nitrogen. After digesting a 0.9814 g sample, the nitrogen contained is oxidized to NH4+, converted to NH3 with NaOH and the NH3 distilled into a collection flask contain 50.00 mL of 0.1047 M HCl. The excess HCl is back titrated with 0.1183 M NaOH, requiring 22.84 mL. What is the % wt protein in the sample given that there is 6.38 g of protein for every gram of nitrogen in the sample.

Question 50

Commercial reagent grade H2SO4 is about