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ACHEM TOPICS > TB_Preparation of Reagents and Chemical Analysis > Flashcards

TB_Preparation of Reagents and Chemical Analysis Flashcards

1
Q

Calculate the equivalent weight and normality for a solution of 6.0 M H3PO4 given the following
reactions:
(a) H3PO4(aq) + 3OH–(aq) PO4
3–
(aq) + 3H2O(l)
(b) H3PO4(aq) + 2NH3(aq) HPO4
2–
(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

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

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2
Q

What is the molality of solution made by dissolve 25 g of NaCl in to 2.0 Liter 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

A

d. 0.214 m

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3
Q

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

a. Complete (or ultimate) analysis

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4
Q

Implies that the constituent determined was present in high concentration
a. Trace analysis
b. Macro analysis
c. Elemental analysis
d. All of the above

A

b. Macro analysis

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5
Q

Quantitative chemicall analysis of weighing a sample, usually of a separated and dried precipitate.
a. Titrimetric analysis
b. Volumetric analysis
c. Gravimetric analysis
d. Elemental analysis

A

c. Gravimetric analysis

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6
Q

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

A

d. ACS grade

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7
Q

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

A

d. Potassium hydrogen phthalate

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8
Q

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

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9
Q

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

A

b. Precise but not accurate

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10
Q

How many grams of Sodium Persulfate (Na2S2O8) required to prepare a 1 L solution of Sodium
Persulfate with concentration of 10% (w/v). This solution is widely used as 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. 100 g of Sodium Persulfate

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11
Q

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%

A

d. 5.10%

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12
Q

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

A

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

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13
Q

Bidirectional harpoons or double arrows (⇆) should be used to indicate ________ reactions
a. one sided
b. resonance
c. dynamic
d. reversible

A

d. reversible

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14
Q

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. 101.29

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15
Q

A few ways in which solution composition can be described are as follows.
a. Molarity
b. Normality
c. Molality
d. All of the above

A

d. All of the above

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16
Q

The substance which does the dissolving and must be greater than 50% of the solution.
a. solvent
b. solute
c. mixture
d. solution

A

a. solvent

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17
Q

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

b. 2.1858

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18
Q

Used to measure volumes approximately, typically with errors of several percent except for one.
a. Beakers
b. pipettes
c. reagent bottles
d. graduated cylinders

A

c. reagent bottles

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19
Q

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

a. 0.1187 M, 7359.05 ppm

20
Q

The number of formula mass of any solute dissolved in 1 liter of solution
a. formality
b. normality
c. molality
d. molarity

A

a. formality

21
Q

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
equivalence point? HgO + 4 I− + H2O →HgI4 2- + 2 OH−
a. 1.0 mL
b. 10 mL
c. 20 mL
d. 50 mL

A

c. 20 mL

22
Q

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

a. 78.2%

23
Q

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

a. primary standard

24
Q

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 .250 M HNO3?
a. 1.58
b. 1.582
c. 1.50
d. 1.583

A

a. 1.58

25
Q

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 ; Lithiumg

A

b. 18.3 g N; Lithium

26
Q

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

A

c. Na2CO3

27
Q

When making a solution from a solid reagent, if necessary, dry the solid reagent on a clean, oven
dried, watch glass at 105 ºC for 2 hours and cool it in a desiccator.
a. 121 ºC
b. 105 ºC
c. 80 ºC
d. 118 ºC

A

b. 105 ºC

28
Q

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

A

d. All of the above

29
Q

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

A

b. equivalence

30
Q

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

A

d. all of the above

31
Q

Boiling occur if the vapor pressure of the liquid is less than the atmospheric pressure.
a. True
b. False
c. not all the time
d. Always

A

b. False

32
Q

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

a. directly proportional

33
Q

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

34
Q

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

A

b. semipermeable membrane

35
Q

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

A

c. osmotic pressure

36
Q

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

A

d. fractional crystallization

37
Q

Which has a lower freezing point?
a. water
b. NaCl
c. NaCl solution
d. all of the above

A

c. NaCl solution

38
Q

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 gram

A

a. the limiting reagent

39
Q

Which of the following hastens the rate of solution?
a. pulverization
b. scratching the sides of the container
c. seeding
d. cooling

A

a. pulverization

40
Q

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
d. Hund’s rule

A

b. the “like dissolves like” rule

41
Q

A solution is _______ if more solute can dissolve in it.
a. saturated
b. supersaturated
c. unsaturated
d. concentrated

A

c. unsaturated

42
Q

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

A

b. solubility

43
Q

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

a. greater than or equal to

44
Q

Which of the following concentration units is independent of temperature?
a. molarity
b. normality
c. molality
d. percent volume

A

c. molality

45
Q

The recommended procedure for preparing a very dilute solution is not to weigh out a very small mass or
measuring a very small volume of a stock solution. Instead it is done by a series of dilutions. A sample of
0.8214 g of KMnO4 (158.04) was dissolved in water and made up to the volume in a 500-ml volumetric
flask. A 2.000-ml sample of this solution was transferred to a 1000-ml volumetric flask and diluted to the
mark with water. Next, 10.00 ml of the diluted solution were transferred to a 250-ml flask and diluted to
the mark with water.
What is the concentration (in molarity) of the final solution?
a. 0.1039 M
b. 2.079 x 10‒5 M
c. 8.316 x 10‒7 M
d. none of the above

A

c. 8.316 x 10‒7 M

46
Q

Calculate the mass of KMnO4 needed to directly prepare the final solution
a. 3.28 x 10‒5 g
b. 6.57 x 10‒5 g
c. 0.4107 g
d. 0.2054 g

A

a. 3.28 x 10‒5 g

ACHEM TOPICS (12 decks)

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