Riverside City College
Test – 02
Chem 1A (Spring)
Name:
Full Marks: 35
SID No:
Time: 1.20 hr
Date: 04/23/2015
Part I: 1 Mark for each of the questions from Q 1 – Q 11. 3 Marks for each of the questions from Q 12 – Q
23. Answer all questions from Part I and 8 out of 12 questions from Part II. Formula and related
data are provided in the back.
______________________________________________________________________________
Part I
1. The gas law that states that the volume of a gas is directly proportional to its amount in
moles under conditions of constant pressure and temperature is known as
2. Calculate the root mean square velocity of nitrogen molecules at 20.0 °C.
1.60 m/s
2.27 m/s
16.2 m/s
133 m/s
511 m/s
3. How many quantum numbers are required to designate a particular orbital?
1
2
3
4
5
4. Which of the following statements about the Bohr model of the hydrogen atom is false?
a) The energy of each Bohr orbit is quantized.
b) An electron in a stationary state does not emit radiation.
c) Transitions between stationary states that are close together require shorter wavelength
that those that are spaced further apart.
d) When an electron jumps to a higher state, energy is absorbed.
e) When an electron falls to a lower state, energy is emitted.
f) All of the above are correct.
5. Two radio stations broadcast at the following frequencies:
Station 1: 107.5 MHz Station 2: 98.1 MHz
a) Station 1 has the longest wavelength.
b) Station 2 has the smallest energy.
1
c) Station 1 broadcasts with the largest amplitude.
d) The wave broadcast by Station 2 moves slower than that broadcast by Station 1
6. Which of the following statements about an ideal gas is false?
a) An ideal gas is a theoretical gas.
b) In an ideal gas, the volume of the gas particles is insignificant compared to the volume
of the container.
c) The molecules of an ideal gas are considered to be point masses.
d) Molecules in an ideal gas do not interact with each other.
e) Molecules in an ideal gas have inelastic collisions.
7. When 1 mole of gas is placed under STP conditions, what is the volume?
i) 0.000 L
ii) 1.00 L
iii) 24.5 L
iv) 22.4 L
v) Not enough information
8. Hard water often contains dissolved [Mg]2+ ions. Some laundry detergents contain sodium
phosphate to soften hard water and to control acidity, thus making the detergent more
effective. What solid product forms when aqueous solutions of sodium phosphate and
magnesium chloride are combined?
i) NaCl
ii) Mg3[PO4]2 iii) MgCl2 iv) Na3PO4
v) Two solids form in this reaction
v) No solid forms in this reaction
9. Under which of the following conditions is a gas least likely to be ideal?
a) high pressure, low temperature
b) low pressure, high temperature
c) high pressure, high temperature
d) low pressure, low temperature
10. In which of the following does nitrogen have the largest positive value for its oxidation
number?
i) NO2
ii) N2
iii) NH3
iv) N2O5
2
11. When heated, potassium chlorate decomposes to potassium chloride and molecular
oxygen: 2KClO3 → 2KCl + 3O2. How much oxygen could be formed from 5.0 g of potassium
chlorate?
i) 28.7 g
ii) 0.061 g
iii) 2.0 g
iv) 1.3 g
v) 0.98 g
Part II
12. We can obtain titanium metal from its oxide according to the following balanced equation:
When 28.6 kg of C reacts with 88.2 kg of TiO2, 42.8 kg of Ti is produced. Find the limiting
reactant, theoretical yield (in kg), and percent yield. (molar mass of TiO2 = 79.87 g/ mol
and molar mass of Ti = 47.87 g/mol)
13. A sample of gas has a mass of 827 mg. Its volume is 0.270 L at a temperature of 88 °C and a
pressure of 975 mmHg. Find its molar mass.
3
14. If you dissolve 25.5 g KBr in enough water to make 1.75 L of solution, what is the molarity
of the solution? (molar mass of KBr = 119.00 g/mol)
15. What volume does 0.556 mol of gas occupy at a pressure of 715 mmHg and a temperature
of 58 °C?
16. What are the quantum numbers and names (for example, 2s, 2p) of the orbitals in the n = 3
principal level? How many n = 3 orbitals exist?
4
17. A balloon is filled with 1.5 moles of helium at room temperature, 25 °C, and has a volume
of 2.4 L. Calculate the volume of the balloon when it is placed into liquid nitrogen at –196
°C. Assume that the pressure remains constant.
18. A 12.5 L scuba diving tank contains a helium–oxygen (heliox) mixture made up of 24.2 g of
He and 4.32 g of O2 at 298 K. Calculate the mole fraction and partial pressure of each
component in the mixture and the total pressure of the mixture.
5
19. When an electron in a hydrogen atom moves from n = 6 to n = 5, light with what
wavelength is emitted?
20. A common way to make hydrogen gas in the laboratory is to place a metal such as zinc in
hydrochloric acid. The hydrochloric acid reacts with the metal to produce hydrogen gas,
which is then collected over water. Suppose a student carries out this reaction and collects a
total of 154.4 mL of gas at a pressure of 742 mmHg and a temperature of 25 °C. What mass
of hydrogen gas (in mg) does the student collect?
6
21. To what volume should you dilute 0.200 L of a 15.0 M NaOH solution to obtain a 3.00 M
NaOH solution?
22. Assign an oxidation state to each atom in each element, ion, or compound.
a. Cr b. Cr3+ c. CCl4 d. SrBr2 e. SO3 f. NO3−
23. Calculate the wavelength of an electron traveling with a speed of 2.65 × 10 6 m/s.
(1 J = 1 kg · m2/s2).
7
En = –2.18 × 10–18 J(1/n2)
Molar mass NO = 30.01 g/mol
Molar mass H2 = 2.02 g/mol
λ = Wavelength
ν = Frequency
Speed of light (c) = 3.00 × 108 m/s
Planck’s Constant, (h) = 6.626 × 10−34 J ∙ s.
Mass of an electron = 9.109x10-31 kg
Energy of an orbital, En = –2.18 × 10–18 J(1/n2)
Molarity (M) = No of Moles / Volume in L
Ideal Gas Constant (R)= 0.08206 L. atm/mol. K or 8.314 J/K. mol
Mol. Wt of Oxygen = 32.0 g/mol
Mol. Wt of Nitrogen = 28.02/mol
8
Element
Symbol
Atomic
number
Atomic
weight
hydrogen
H
1
1.008
helium
He
2
4.003
lithium
Li
3
6.941
carbon
C
6
12.011
nitrogen
N
7
14.007
oxygen
O
8
15.999
fluorine
F
9
18.998
neon
Ne
10
20.18
sodium
Na
11
22.99
magnesium
Mg
12
24.305
Al
13
26.982
silicon
Si
14
28.086
phosphorus
P
15
30.974
S
16
32.065
chlorine
Cl
17
35.453
argon
Ar
18
39.948
potassium
K
19
39.098
calcium
Ca
20
40.078
krypton
Kr
36
83.8
aluminum
(aluminium)
sulfur
(sulphur)
9