ChTLE 2024 Test Bank 5 (Preparation of Reagents and Chemical Analysis)

Calculate the equivalent weight and normality for a solution of 6.0 M H3PO4 given the following reactions:

(a) H3PO4(aq) + 3OH-(aq) --> PO43-(aq) + 3H2O(l)

(b) H3PO4(aq) + 2NH3(aq)--> HPO42-(aq) + 2NH4+(aq)

(c) H3PO4(aq) + F-(aq) --> H2PO4-(aq) + HF(aq)

a. (a) 18 N, (b) 12 N and (c) 6N

b. (a) 12 N, (b) 18 N and (c) 6N

c. (a) 6 N, (b) 12 N and (c) 18N

d. (a) 16 N, (b) 12 N and (c) 3N

A.

What is the molality of solution made by dissolve 25 g of NaCl in to 2.0 L of water? Assume the density of water d = 1.0 g/mL (= kg/L).

a. 0.210 m

b. 0.250 m

c. 0.211 m

d. 0.214 m

D.

The amounts of all constituents in the samples were determined.

a. Complete (or ultimate) analysis

b. Partial analysis

c. Elemental analysis

d. All of the above

A.

Implies that the constituent determined was present in high concentration.

a. Trace analysis

b. Macro analysis

c. Elemental analysis

d. All of the above

B.

Quantitative chemical analysis of weighing a sample, usually of a separated and dried precipitate.

a. Titrimetric analysis

b. Volumetric analysis

c. Gravimetric analysis

d. Elemental analysis

C.

A chemical grade of highest purity and meets or exceeds purity standards set by American Chemical Society.

a. Technical grade

b. Laboratory grade

c. Pure or practical grade

d. ACS grade

D.

Which of the following is a primary standard for use in standardizing bases?

a. Ammonium hydroxide

b. Sulfuric acid

c. Acetic acid

d. Potassium hydrogen phthalate

D.

How would you prepare 500.0 mL of 0.2500 M NaOH solution starting from a concentration of 1.000 M?

a. Transfer 125 mL from initial solution (1.000 M) and complete with solvent to 500.0 mL.

b. Transfer 121 mL from initial solution (1.000 M) and complete with solvent to 500.0 mL.

c. Transfer 122 mL from initial solution (1.000 M) and complete with solvent to 500.0 mL.

d. Transfer 112 mL from initial solution (1.000 M) and complete with solvent to 500.0 mL.

A.

A student performs five titrations and obtains a mean result of 0.110 M, with a standard deviation of 0.001 M. If the actual concentration of the titrated solution is 0.100 M, which of the following is true about the titration results?

a. Accurate but not precise

b. Precise but not accurate

c. Both accurate and precise

d. Neither accurate nor precise

B.

How many grams of Sodium Persulfate (Na2S2O8) is required to prepare a 1 L solution of Sodium Persulfate with a concentration of 10% (w/v)? This solution is widely used as an oxidizing reagent for Total Organic Carbon analyzer (TOC).

a. 100 g of Sodium Persulfate

b. 101 g of Sodium Persulfate

c. 102 g of Sodium Persulfate

d. 99 g of Sodium Persulfate

A.

A solution has been prepared by transfer 60 mL from Ortho-phosphoric acid 85 % (v/v) H3PO4 and dilute to 1.0 L. What is the concentration of the new solution?

a. 10.10%

b. 9.25%

c. 12.2%

d. 5.10%

D.

A student has got three stock standard solutions of 3 different elements, zinc (Zn) 2000 ppm, cadmium (Cd) 1500 ppm and lead (Pb) 1000 ppm. A student took 10 mL from each solution and transfers it to 200 mL volumetric flask then completed to total volume with solvent. What is the final concentration of each element in the diluted mix solution?

a. 50 ppm Zinc, 32 ppm Cd, 25 ppm Pb

b. 100 ppm Zinc, 75 ppm Cd, 50 ppm Pb

c. 75 ppm Zinc, 75 ppm Cd, 50 ppm Pb

d. 100 ppm Zinc, 25 ppm Cd, 25 ppm Pb

B.

Bidirectional harpoons or double arrows (⇆) should be used to indicate ________ reactions.

a. one sided

b. resonance

c. dynamic

d. reversible

D.

In the preparation of 1 liter of 1.0 N acid from 35% Hydrochloric Acid, what weight of the impure acid should be taken, assuming standardization in the recommended manner?

a. 101.29

b. 113.29

c. 111.29

d. 124.89

A.

A few ways in which solution composition can be described are as follows.

a. Molarity

b. Normality

c. Molality

d. All of the above

D.

The substance which does the dissolving and must be greater than 50% of the solution.

a. solvent

b. solute

c. mixture

d. solution

A.

Naphthalene (C10H8) is one of aromatic hydrocarbons measured by GC-MS. If molecular weight of naphthalene is 128.6 g/mol; how many milligrams are required to prepare 100 mL of 2,000 ppb stock standard solution of naphthalene from powder Naphthalene (purity of 91.5 % w/w)?

a. 2.18

b. 2.1858

c. 2.186

d. 2.1859

A.*

A student has to measure out 9.40 mL of a liquid and selects a 100-mL graduated cylinder. To improve the accuracy of the measurement, it would be most effective to:

a. take the average of multiple measurements using the graduated cylinder.

b. measure the liquid using a 25 mL graduated cylinder instead.

c. estimate the measurement obtained from the graduated cylinder to an additional significant figure.

d. measure the liquid using a 10 mL graduated pipette instead.

D.

Nitrate (NO3-) anion solution prepared by dissolving 3.0 g of KNO3 in 250 mL of water. What is the concentration of Nitrate ion, express the concentration in Molarity and ppm.

a. 0.1187 M, 7359.05 ppm

b. 0.1190 M, 7349.05 ppm

c. 0.1107 M, 7459.00 ppm

d. 0.1120 M, 7400.00 ppm

A.

The number of formula mass of any solute dissolved in 1 liter of solution.

a. formality

b. normality

c. molality

d. molarity

A.

A 0.217 g sample of HgO (molar mass = 217 g) reacts with excess iodide ions according to the reaction. Titration of the resulting solution requires how many mL of 0.10 M HCl to reach the equivalence point?

HgO + 4 I− + H2O →HgI4 2- + 2 OH−

a. 1.0 mL

b. 10 mL

c. 20 mL

d. 50 mL

C.

If the theoretical yield for a reaction was 156 grams and I actually made 122 grams of the product, what is my percent yield?

a. 78.2%

b. 128%

c. 19.0%

d. none of these

A.

The method of standardization can be used if a_________ reacts quantitatively with the reagent needed in the standard solution.

a. primary standard

b. secondary standard

c. working standards

d. intermediate solution

A.

You have a stock solution of 15.8 M HNO3. How many mL of this solution should you dilute using only a graduated pipette to make 100.0 mL of 0.250 M HNO3?

a. 1.58

b. 1.582

c. 1.50

d. 1.583

A.

If 56.0 g of Li reacts with 56.0 g of N2, 93.63 grams of Li3N can be produced. How many grams of Nitrogen remains? What is the limiting reactant?

a. 19.3 g; Nitrogen

b. 18.3 g N; Lithium

c. 20.3 g N; none

d. 18.39 ; Lithium

B.

HCl cannot be considered to be a primary standard because of its gaseous form at room temperature, but its solutions may be standardized against anhydrous ______.

a. NaSO4

b. NaHCO3

c. Na2CO3

d. All of the above

C.

When making a solution from a solid reagent, if necessary, dry the solid reagent on a clean, oven dried, watch glass at ____ ºC for 2 hours and cool it in a desiccator.

a. 121 ºC

b. 105 ºC

c. 80 ºC

d. 118 ºC

B.

Requirements of a primary standards.

a. High Purity, 99.9% or better

b. Stability in air

c. Absence of hydrate water

d. All of the above

D.

Blank samples are prepared so that you have a measure of the amount that needs always to be added to or subtracted from the end point to achieve the ________point.

a. titration error

b. equivalence

c. accuracy

d. precision

B.

Property which depends on the number of particles dissolved in a given mass of solvent.

a. vapor pressure lowering

b. boiling point elevation

c. freezing point depression

d. all of the above

D.

Boiling occurs if the vapor pressure of the liquid is less than the atmospheric pressure.

a. True

b. False

c. not all the time

d. Always

B.

What is the relationship between the temperature and the solubility of a solid in a liquid?

a. directly proportional

b. inversely proportional

c. no relationship

d. geometric

A.

What is boiling point elevation?

a. it is the difference between the boiling points of a pure solvent and a solution

b. it is the sum of the boiling points of a pure solvent and a solution

c. it is the difference between the boiling points of a pure solute and a pure solvent

d. it is the boiling point of a solution

A.

A membrane that allows the passage of solvent molecules through but not solute molecules is called:

a. animal membrane

b. semipermeable membrane

c. permeable membrane

d. plant membrane

B.

The excess pressure required to stop the flow and keep the solution in equilibrium with the pure solvent is:

a. partial pressure

b. vapor pressure

c. osmotic pressure

d. atmospheric pressure

C.

The separation of a mixture of substances into pure components on the basis of their differing solubilities is:

a. fractional distillation

b. vacuum crystallization

c. vacuum distillation

d. fractional crystallization

D.

Which has a lower freezing point?

a. water

b. NaCl

c. NaCl solution

d. all of the above

C.

The reactant which is present in the smallest stoichiometric amount and which limits the amount of product that can be formed in a reaction is:

a. the limiting reagent

b. the reagent with the least number of grams

c. the excess reagent

d. the reagent with the most number of grams

A.

Which of the following hastens the rate of solution?

a. pulverization

b. scratching the sides of the container

c. seeding

d. cooling

A.

A polar solute usually dissolves in a polar solvent and a nonpolar solute usually dissolves in a nonpolar solvent. This is:

a. the solubility rule

b. the "like dissolves like" rule

c. Henry's law

B.

A solution is ______________ if more solute can dissolve in it.

a. saturated

b. supersaturated

c. unsaturated

d. concentrated

C.

The maximum amount of solute that will dissolve in a definite amount of solvent to produce a stable system at a specified temperature is called:

a. dilution

b. solubility

c. saturation

d. concentration

B.

The normality of a solution is always the molarity.

a. greater than or equal to

b. greater than

c. less than or equal to

d. less than

A.

Which of the following concentration units is independent of temperature?

a. molarity

b. normality

c. molality

d. percent volume

C.