pracexam2

Practice exam 2 Chem 1A
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Balance the following redox equation using the smallest integers possible and select the correct coefficient for the iron(II) hydroxide, Fe(OH)₂.
Fe(OH)₂(s) + CrO₄2-(aq) → Fe₂O₃(s) + Cr(OH)₄-(aq) + H₂O(l) + OH^-(aq)

Which one of the following is not a redox reaction?

A.	2H₂O₂(aq) → 2H₂O(l) + O₂(g)

B.	N₂(g) + 3H₂(g) → 2NH₃(g)

C.	BaCl₂(aq) + K₂CrO₄(aq) → BaCrO₄(aq) + 2KCl(aq)

D.	2Al(s) + Fe₂O₃(s)→ Al₂O₃(s)+ 2Fe(s)

E.	2H₂O(g) → 2H₂(g) + O₂(g)

Which one of the following substances is the best electrolyte?

CH₃Cl

CH₄

C₂H₅OH

HCl

Select the classification for the following reaction.
H₂(g) + Cl₂(g) → 2HCl(g)

A.	combination

B.	decomposition

C.	displacement

acid-base

E.	none of the above

In the following reaction, what ions, if any, are spectator ions?
Pb(NO₃)₂(aq) + 2NaCl(aq) → PbCl₂(s) + 2NaNO₃(aq)

A.	Pb²⁺(aq), Cl^-(aq)

B.	Na⁺(aq), NO₃-(aq)

C.	Pb²⁺(aq), NO₃-(aq)

D.	Na⁺(aq), Cl^-(aq)

E.	There are no spectator ions

Which of the following is a weak acid?

H₂SO₄

HNO₃

HBr

HCl

Which of the following will be least soluble in water?

A.	potassium sulfate, K₂SO₄

B.	ammonium nitrate, NH₄NO₃

C.	chloromethane, CH₃Cl

D.	calcium chloride, CaCl₂

E.	ethanol, C₂H₆O

8.	a. Explain or define what is meant by the term “oxidation.” b. Write down the oxidation numbers of the atoms in the following formulas. K₂Cr₂O₇NaH K: Cr: O: Na: H: Answer:

The combustion of an element is always a combination reaction.

True

False

10.

The oxidation numbers of P, S and Cl in H₂PO₂^-, H₂S and KClO₄ are, respectively

A.	-1, -1, +3

B.	+1, -2, +7

C.	+1, +2, +7

D.	-1, -2, +7

E.	-1, -2, +3

11.

Calculate the oxidation number of iodine in I₂.

-1

E.	none of the above is the correct oxidation number

12.

Sulfuric acid (H₂SO₄) reacts with potassium hydroxide (KOH) as follows.
H₂SO₄(aq) + 2KOH(aq) → K₂SO₄(aq) + 2H₂O(l)
Calculate the volume of 0.100 M sulfuric acid required to neutralize 25.0 mL of 0.0821 M KOH. Show all your work.

Answer:

13.

Select the classification for the following reaction.
2I^-(aq) + Cl₂(aq) → I₂(aq) + 2Cl ^-(aq)

A.	combination

B.	displacement

C.	decomposition

D.	precipitation

acid-base

14.

Select the classification for the following reaction.
2H₂O₂(aq) → 2H₂O(l) + O₂(g)

A.	combination

B.	decomposition

C.	displacement

acid-base

E.	none of the above

15.

Write down the oxidation number of the indicated atom in each of the following formulas:
a. Si in SiO₂
b. Cl in ClO₂-
c. Mn in KMnO₄
d. C in C₆H₁₂O₆

Answer:

16.

Which of the following gases effuses most rapidly?

nitrogen

oxygen

C.	hydrogen chloride

ammonia

E.	carbon monoxide

17.

Use the van der Waals equation for real gases to calculate the pressure exerted by 1.00 mole of ammonia at 27°C in a 750-mL container. (a = 4.17 L²atm/mol², b =0.0371 L/mol)

23.2 atm

27.1 atm

32.8 atm

42.0 atm

32.8 torr

18.

State Charles's Law and illustrate it with a graph, using standard x-y coordinate axes. Be sure to label the axes unambiguously with the correct gas variables.

Answer:

19.

What are the conditions of STP?

A.	0 K and l atm

B.	273.15 K and 760 torr

C.	0°C and 760 atm

D.	273.15°C and 760 torr

E.	none of the above

20.

Select the gas with the largest root-mean-square molecular speed at 25°C.

NH₃

H₂

SF₆

E.	All the gases have the same root-mean-square molecular speed at 25°C.

21.

Small quantities of hydrogen can be prepared by the addition of hydrochloric acid to zinc. A sample of 195 mL of hydrogen was collected over water at 25°C and 753 torr. What mass of hydrogen was collected? (P_water = 24 torr at 25°C)

0.00765 g

0.0154 g

0.0159 g

0.0164 g

0.159 g

22.

The temperature of the carbon dioxide atmosphere near the surface of Venus is 475°C. Calculate the average kinetic energy per mole of carbon dioxide molecules on Venus.

A.	2520 J/mol

B.	4150 J/mol

C.	5920 J/mol

D.	9330 J/mol

E.	5920 kJ/mol

23.

A flask containing neon gas is connected to an open-ended mercury manometer. The open end is exposed to the atmosphere, where the prevailing pressure is 745 torr. The mercury level in the open arm is 50. mm below that in the arm connected to the flask of neon. What is the neon pressure, in torr?

-50. torr

50. torr

695 torr

795 torr

E.	none of the above

24.

Assuming ideal behavior, what is the density of argon gas at STP, in g/L?

A.	0.0176 g/L

B.	0.0250 g/L

C.	0.0561 g/L

1.78 g/L

181. g/L

25.

Aluminum metal shavings (10.0 g) are placed in 100. mL of 6.00 M hydrochloric acid. What is the maximum volume of hydrogen, measured at STP, which can be produced?
2Al(s) + 6HCl(aq) → 2AlCl₃(aq) + 3H₂(g)

Answer:

26.

A sample container of carbon monoxide occupies a volume of 435 mL at a pressure of 785 torr and a temperature of 298 K. What would its temperature be if the volume were changed to 265 mL at a pressure of 785 torr?

182 K

298 K

387 K

489 K

538 K

27.

Arrange the following gases in order of increasing rate of effusion.
C₂H₆, Ar, HCl, PH₃

A.	Ar < HCl <PH₃< C₂H₆

B.	C₂H₆< PH₃< HCl < Ar

C.	Ar < PH₃< C₂H₆< HCl

D.	C₂H₆< HCl < PH₃< Ar

E.	Ar <PH₃< HCl< C₂H₆

28.

A 1.00-L sample of a pure gas weighs 0.785 g and is at 0.965 atm and 29.2°C.
a. What is the molar mass of the gas?
b. If the volume and temperature are kept constant while 0.400 g of the same gas are added to that already in the container, what will the new pressure be?

Answer:

29.

The pressure of hydrogen sulfide gas in a container is 35,650 Pa. What is this pressure in torr?

A.	46.91 torr

B.	267.4 torr

C.	351.8 torr

3612 torr

E.	27090 torr

30.

What is the density of carbon dioxide gas at -25.2°C and 98.0 kPa?

0.232 g/L

0.279 g/L

0.994 g/L

1.74 g/L

2.09 g/L

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