Answers25-26 KCS18 Chemistry ICUnit Test

Unit Test — Unit test Answers

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What type of substance reacts with limestone (CaCO3) and produces carbon dioxide gas?

A
a neutral substance
B
a base
C
an acid
D
both an acid and a base
2
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A number of beakers have different concentrations of a solution. Which statement best describes the most concentrated solution?

A
It has the largest volume.
B
It has the most solute for a given volume.
C
It has the greatest amount of solute.
D
It has the most volume for a given amount of solute.
3

Soaps feel slippery on our hands because they dissolve the oil on our skin, decreasing friction.This is because soap contains

A
a neutral molecule.
B
a salt molecule.
C
an acid.
D
a base.
4

The molality of a solution that is made by dissolving a certain mass of ethanol in 85.4 g of water is 0.950 m. How many moles of ethanol were dissolved?Use .

Question illustration
A
0.0811 mol
B
0.0899 mol
C
11.1 mol
D
81.1 mol
5

Which of these correctly defines the pOH of a solution?

A
the log of the hydronium ion concentration
B
the negative log of the hydronium ion concentration
C
the log of the hydroxide ion concentration
D
the negative log of the hydroxide ion concentration
6

Which solute, an electrolyte or a nonelectrolyte, has the greater effect on the boiling point when a given amount of each solute is dissolved in the same mass of water?

A
The nonelectrolyte does because it disperses into molecules.
B
The electrolyte does because it disperses into molecules.
C
The nonelectrolyte does because it dissociates into ions.
D
The electrolyte does because it dissociates into ions.
7

A government laboratory wants to determine whether water in a certain city has any traces of fluoride and whether the concentration exceeds the recommended 4.00 ppm. A 5.00-g sample of this water is found to have 0.152 mg of fluoride. Should the water be declared safe for drinking?Use .

Question illustration
A
3.04 ppm < 4.00 ppm, safe to drink
B
7.60 ppm > 4 ppm, safe to drink
C
A. 30.4 ppm > 4 ppm, unsafe to drink
D
30,400 ppm > 4 ppm, unsafe to drink
8

What is the relationship between the concentration of particles in a solution and the solution’s vapor pressure?

A
As solute concentration increases, vapor pressure increases.
B
As solute concentration increases, vapor pressure decreases.
C
As the concentration of electrolytes increases, vapor pressure increases. However, as the concentration of nonelectrolytes increases, vapor pressure decreases.
D
As the concentration of electrolytes increases, vapor pressure decreases. However, as the concentration of nonelectrolytes increases, vapor pressure increases.
9

Which of the following substances is an Arrhenius acid?

A
BF3
B
HCN
C
NH3
D
Mg(OH)2
10

In a coffee shop, the following coffee samples are prepared for customers.i. 10 g of sugar added to 100 g of coffeeii. 10 g of sugar added to 200 g of coffeeiii. 4 g of sugar added to 200 g of coffeeiv. 4 g of sugar added to 100 g of coffeeBased on the amount of sugar added, which sequence ranks the coffee from the sweetest coffee to the least-sweet coffee?

A
i, ii , iii, iv
B
iii, iv, ii, i
C
iv, i, ii, iii
D
i, ii, iv, iii
11

Lewis acids and bases are most closely associated with which process?

A
proton transfer
B
electron transfer
C
the formation of aqueous ions
D
the formation of a conjugate acid or base
12

Which description correctly characterizes the acidity or basicity of a solution?

A
The higher the pH is, the more the hydroxide ion concentration decreases and the more acidic the solution becomes.
B
The higher the pH is, the more the hydroxide ion concentration increases and the more basic the solution becomes.
C
The lower the pH is, the more the hydronium ion concentration decreases and the more acidic the solution becomes.
D
The lower the pH is, the more the hydronium ion concentration increases and the more basic the solution becomes.
13

What mass of solid that has a molar mass of 46.0 g/mol should be added to 150.0 g of benzene to raise the boiling point of benzene by 6.28°C? (The boiling point elevation constant of benzene is 2.53°C•kg/mol.)Use .

Question illustration
A
2.48 g
B
8.25 g
C
17.1 g
D
43.3 g
14

Consider the reaction below.NH4+ + H2O NH3 + H3O+Which is an acid-conjugate base pair?

Question illustration
A
NH4+ and NH3
B
NH4+ and H3O+
C
H2O and NH3
D
H2O and H3O+
15

What is the molality of a solution that is obtained by dissolving 2.922 g of NaCl into 1000.0 g of water if the molar mass of NaCl is 58.44 g/mol?Use .

Question illustration
A
0.05000 m
B
2.922 m
C
5.856 m
D
20.00 m
16

A 250-mL aqueous solution contains 1.56 10–5 g of methanol and has a density of 1.03 g/mL. What is the concentration in ppm?Use .

Question illustration
A
6.1 10-8 ppm
Option A
B
1.5 10-5 ppm
Option B
C
0.061 ppm
D
15 ppm
17

What is the definition of a Lewis base?

A
a substance that donates a proton
B
a substance that donates electrons to form a covalent bond
C
a substance that accepts electrons to form a covalent bond
D
a substance that when dissolved in water increases hydrogen ion concentration
18

An unknown substance turns blue litmus paper to red. Which additional test could be used to confirm the substance’s identity?

A
It should turn phenolphthalein from colorless to pink because it is a base.
B
It should turn phenolphthalein from pink to colorless because it is a base.
C
It should turn methyl orange to orange because it is an acid.
D
It should turn methyl orange to red because it is an acid.
19

Which pair of substances would most likely result in the production of a gas when reacting with an acid?

A
litmus and methyl orange
B
base and salt
C
metal and carbonate
D
carbon dioxide and water
20

What mass of solid that has a molar mass 89.0 g/mol should be added to 100.0 g of benzene to raise the boiling point of benzene by 2.42°C? (The boiling point elevation constant of benzene is 2.53°C•kg/mol.)Use .

Question illustration
A
2.84 g
B
8.52 g
C
21.5 g
D
93.0 g

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