REVISION FOR TEST 1 CHEF114 T2 2011/2012
Question 1
(a)
(b)
The element oxygen has three (3) naturally occurring isotopes with 8, 9 and 10
neutrons in the nucleus, respectively.
(i)
Write the full chemical symbols for these three isotopes. [3 marks]
(ii)
State one (1) similarity and one (1) difference between these isotopes. [2
marks]
Fill in the table below with the correct chemical formulas: [5 marks]
Chemical formula
Name
Nitrogen trifluoride
Copper(I) cyanide
Iodic acid
Silver chromate
Nickel(II) nitrate hexahydrate
Question 2
Ethyl acetate, CH3CO2C2H5, is the solvent in many fingernail polish removers. It is prepared
by the reaction of ethanol, C2H5OH, with acetic acid, CH3CO2H; the other product is water.
A small amount of sulfuric acid, H2SO4 is used to accelerate the reaction, but the sulfuric acid
is not consumed and does not appear in the balanced equation. Suppose you are given 10.0
mL each of acetic acid and ethanol:
[Given: The densities of acetic acid, ethanol and ethyl acetate are 1.0492 g/mL, 0.7893 g/mL
and 0.9003 g/mL, respectively. The molar masses of acetic acid, ethanol and ethyl acetate are
60.05 g/mol, 46.07g/mol, and 88.11 g/mol, respectively].
C2H5OH + CH3CO2H  CH3CO2C2H5 + H2O
(a)
Which is the limiting reactant in this reaction?
(b)
How many mL of ethyl acetate can be prepared using this reaction?
(c)
Which is the excess reactant in this reaction? How many moles of the excess reactant
remains at the end of this reaction?
[2 marks]
1
[5 marks]
[3 marks]
Question 3
(a)
Combining Boyle’s Law, Charles’ Law and Avogadro’s Law gives the ideal gas
equation. Derived the ideal gas equation using the above three laws. [5 marks]
(b)
Acetylene, C2H2, is an important fuel in welding. It is produced in the laboratory when
calcium carbide, CaC2, reacts with water:
CaC2(s) + 2H2O(l) → C2H2(g) + Ca(OH)2(s)
A sample of acetylene, C2H2 was collected over water at 23oC. The total gas pressure
was 748 mmHg and the volume was 543 mL. At 23oC, the vapour pressure of water
is 21 mmHg. What mass of acetylene in g was collected? [5 marks]
Question 4
a)
An element with three stable isotopes has 82 protons. The separate isotopes contain
124, 125, 126 neutrons. Identify the element, and write symbols for the isotopes. [3
points]
b)
c)
Write the chemical name for each compound:
(i)
(NH4)3 PO4
:
____________________________
(ii)
Fe(OH)3
:
____________________________
(iii)
IF7
:
____________________________
(iv)
HBrO4
:
____________________________
(v)
Co(ClO3)2·2H2O
:
[5 points]
____________________________
Write the empirical formula for the binary compound formed by the most common
monatomic ions formed by each pair of elements:
(i)
Germanium and oxygen
: ______________________
(ii)
Rubidium and sulfur
: ______________________
2
[2 points]
Question 5
a)
1.056 g of a metal carbonate, containing an unknown metal M, was heated to give the
metal oxide and 0.376 g CO2. The balanced equation for the reaction is as below:
MCO3 (s) + heat → MO (s) + CO2 (g)
What is the identity of the metal M?
b)
[3 points]
A fuel mixture used in the early days of rocketry is composed of two liquids,
hydrazine (N2H4) and dinitrogen tetroxide (N2O4), which ignites on contact to form
nitrogen gas and water vapor.
2 N2H4 (ℓ) + N2O4 (ℓ) → 3 N2 (g) + 6 H2O (g)
If 150.00 g of N2H4 and 200.00 g of N2O4 are mixed, and 155.00 g of N2 are actually
obtained from the reaction, what is the percent yield?
[5 points]
c)
How many grams of solute are there in 100 mL of a 1.023 x 10 -3 M solution of
Na3PO4?
[2 points]
Question 6
a)
An aerosol can with a volume of 0.50 L has a bursting point of 2.6 atm. If the can
contains 1.0 g CO2 and is heated to 400 C, will it burst (Yes or No)? Show (using
calculations) how you arrived at your final answer. [3 points]
b)
Calculate the density, in g/L, of CO2 gas at 27C and 0.50 atm pressure. [3 points]
c)
A sample of mercury(II) oxide is placed in a 5.00 L evacuated container and heated
until it decomposes entirely to mercury metal and oxygen gas. After the container is
cooled to 25 C, the pressure of the gas inside is 1.73 atm.
(i)
Write a balanced equation for the decomposition of mercury(II) oxide
(ii)
What mass of mercury (II) oxide was originally placed in the container?
[4 points]
Question 7
a)
Complete the table below:
Symbol
No. of protons
48
Ti
54
Fe 2+
82
Br -
No. of electrons
No. of neutrons
Net charge
[4 points]
3
b)
Name or give the formulas of the following compounds:
(i)
P4O10
: ___________________
(ii)
CuSO4.5H2O
: ___________________
(iii)
Disilicon hexabromide
: ___________________
(iv)
Manganese (IV) oxide
: ___________________
[2 points]
Question 8
In the reaction below, 79.8 g of Fe2O3 reacts with 45.3 g of CO.
Fe2O3(s) + 3CO(g) → 2Fe(g) + 3CO2(g)
a) Determine the limiting reagent.
[2 points]
b) Calculate the mass of Fe formed.
[2 points]
c) What is the mass of excess reagent leftover after the reaction is completed. [2 points]
Question 9
A sample of liquid nitrogen trichloride, NCl3, was heated in a 2.50-L closed reaction vessel
until it decomposed completely into gaseous elements. The resulting mixture exerted a
pressure of 754 mmHg at 95oC.
(a)
What was the partial pressure of each gas in the container?
(3 points)
(b)
What was the mass of the original sample – the liquid NCl3?
(3 points)
Question 10
a)
b)
A 44-g sample of an unknown metal at 99 oC was placed in a constant-pressure
calorimeter containing 80.0 g of water at 24.0 oC. The final temperature of the system
was found to be 28.4 oC. Calculate the specific heat of the metal. The heat capacity of
the calorimeter is 12.4 J/oC. [3 marks]
Calculate the work done in Joules by the reaction:
2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g)
when 0.34 g of Na reacts with water to form H2 gas at 0o C and 1.0 atm. [3 marks]
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Question 11
a)
The thermochemical equation for the combustion of 2 moles of MgO is as follows:
2 Mg (s) + O2 (g)  2 MgO (s)
H = −1203.6 kJ
What is the Horxn for MgO (s)  Mg (s) + ½ O2(g) ?
b)
[2 marks]
The combustion of one mole of benzene, C6H6, in oxygen liberates 3,268 kJ of heat.
The products of the combustion reaction are carbon dioxide and water.
(i)
Write the complete thermochemical equation for the combustion of two (2)
moles of benzene. [1 marks]
(ii)
How much heat is given off when 183 g of oxygen are reacted with excess
benzene? [3 marks]
c)
At 25C, the following heats of reaction are known:
2 ClF (g) + O2 (g)  Cl2O (g) + F2O
∆Horxn = +167.4 kJ/mol
2 ClF3 (g) + 2 O2 (g)  Cl2O (g) + 3 F2O (g)
∆Horxn = +341.4 kJ/mol
2 F2 (g) + O2 (g)  2 F2O (g)
∆Horxn = –43.4 kJ/mol
Use Hess's law to calculate Horeaction at 25C for the reaction below:
ClF(g) + F2(g)  ClF3(g)
[4 marks]
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