CHM 101 PAST TEST
QUESTIONS
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CHM 101 [2018/2019 PQ]
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(1) Benzene, C6H6 reacts with oxygen, O2, to form CO2 and H2O. How much 02, is
required to complete combustion of 1.0 mole of C6H6?
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Ans: 240g
(2) What is the concentration of nitrate ion in a 425
containing 32.0g of Mg(NO3)2 (m = 148.3)
Ans: 1.02M
(3) The electronic configuration of the element whose atomic number is 26 is?
Ans: [Ar] 4s^2 3d^6
(4) Determine the number of moles of aluminum in 2.154 x 10^-4 Kg.
Ans: 7.98 moles
(5) What is the solubility of MgF2 (Ksp 6.8 x 10^9) in pure water?
Ans: 0.0012M
(6) What is the ratio Kg for the following reaction at 723°C.
O2(g) + 3UO2Cl2 ----> U3O8(s) + 3Cl2(g)
Ans: 81.8 : 1
(7) Calculate the pressure of 0.55mol of NH3 gas in a 2.00L vessel at 25°C using ideal gas
law.
Ans: p = 6.73 atm
(8) A mixture of three gases has a pressure of 1380mHg at 283K. The mixture is analyzed
and is found to contain 1.27mol C02, 3.04mol CO, and 1.50mol, Ar. What is the partial
pressure of Ar?
Ans: 302mmHg
(9 This equation is unbalanced:
PCl + H2O ------> H3PO3 + HCL
Ans: PCl + 3H2O ------> H3PO3 + 3HCL, coefficient of 1:3:1:3
(10) A 20.Oml of an element with a density of 30g/mol contains 4x 104 atoms. What is the
atomic weight of the element?
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Ans: 90g
CHM 101 [2017/2018 PQ] - Sipisi Media
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(1) Determine the ground state electronic configuration of the following atoms with the
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indicated atomic numbers
(a)He
(b) N
© Ne
(d) Mg
Ans: He - 1s^2. ,
N - 1s^2, 2s^2, 2p^3.
Ne - 1s^2, 2s^2, 2p^6,
Mg - 1s^2, 2s^2, 2p^6, 3s^2
(2) A water sample contains 0.43g of iron per litre of water. Express the concentration of
iron in
I. mg per gram
ii. parts per million
Ans:
i) 0.43mg/g
ii) 430ppm
(3 For the reaction between H and I, to give HI, the concentrations of substances present
in the equillibrium mixture at 450°C are as follows:
[H2] = 0.885moldm: ,[I2] = 0.20moldm: [HI] = 0.945moldm. Calculate the Keq at this
temperature.
Ans: Keq = 5.045
(4) A solution of HCl in water is standardized by titrating a solution of 0.5015g sample of
pure, dry sodium carbonate Na2CO3. What is the concentration of the HCl solution if
48.47ml is added from the burette to reach the end point?
Ans: 0.2M
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CHM 101 [2016/2017 PQ] - Sipisi Media
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(1) Balance the equations
i) C5H12 + 11O2 -------> 5CO2 + 12H20
ii) Ba(CIO3)2 -------> BaCl2 + 2O2
Ans:
C5H12 + 8O2 -------> 5CO2 + 6H20
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Ba(CIO3)2 -------> BaCl2 + 3O2
(2) What are the possible value of I and m when n = 3?
Ans: l = 0,1,2.
m = -l to +l, = -2, -1, 0, 1, 2
(3) What is the molarity of a solution made by dissolving 43.7g of anhydrous CusO4 (mw
= 160) to make 2.00dm solution?.
Ans: 0.137M
(4) What is the pH of 0.015M Ca(OH)2 solution..
Ans: 12.48
(5) A gas cylinder of 105x10^3m^3 contain 280g nitrogen gas at 27°C. Calculate the actual
pressure of the gas in pascal…
Ans: 0.2375pa
(6) Calculate the workdone when 4moles of nitrogen gas expands isothermally from
15dm^3 to 50dm^3 against constant pressure of 1atm(101.325Kpa) at 25°C..
Ans: 11931.7J
(7) Write the electronic configuration of 28Ni^2+
Ans: 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^0, 3d^8
(8) Determine the oxidation number of phosphorus in Ca3(PO4)2
Ans: +5
(9) Why is it always the case that 2nd ionization energy is larger that 1st ionization
energy.
Ans: lonization energy is the energy required to remove an electron from an atom.
when the first electron is removed(first ionization energy), the remaining electron
is now more tightly bound to the nucleus because there tend to be reduced
screening effect of inner electrons due to the removal of one electron. In this case,
the remaining electron becomes relatively more difficult to remove hence second
ionization energy is increased.
(10) Calculate the root mean square value for the atom in a sample of Helium gas of
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78.75K.
Ans: Vrms = 700.75m/s
CHM 101 [2015/2016 PQ] - Sipisi Media
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(1) Write the balanced chemical equations of the reactions:
PCl+H2O -------> H3PO4 + HCI.
Ans: PCl + 4H2O -------> H3PO4 + 5HCI.
(2) How many grams of copper Cu are there in 2.55moles of Cu.
Ans: 161.92g
(3) A gaseous compound that contains 27% Carbon and 73% oxygen is a by-product of
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wine making. What is the empirical formular of the compound?
Ans: CO2
(4) How many moles of sulfuric acid, H2SO4 are contained in 0.80L of a 0.05M solution of
sulfuric acid.
Ans: 0.04 moles
(5) Balance the equation: N2H4+ N2O4 ------> N2 + H2O.
Ans: 2N2H4+ N2O4 ------> 3N2 + 4H2O.
(6) Write the electronic configuration of S^2-.
Ans: 1s^2, 2s^2, 2p^6, 3s^2, 3p^6,
(7) Why is it always the case that the 2nd ionization energy is larger than the 1st
ionization energy?.
Ans: since one electron had already been removed from the atom(First ionization),
The atomic size is reduced. Because of this, the net effect of the positive nuclear
charge tends to increase due tO fewer number or electrons available. Thus it
becomes more difficult to remove the left over electons from the atom. NOTE:
The smaller the atomic size, the greater the ionization potential and vice-versa.
Also: lonization energy is the energy required to remove an electron from an atom
to give a positive ion that is a cation.
(8) If the unit cell of NaCl is 5.64A° on an edge, calculate the density of NaCl
Ans: 2.17g/cm3
(9) Which unit cell has a alpha = beta = gamma = 90?.
Ans: Rhombohedral
(10) If the work done by a system is equal to zero, what expression is used to describe it?
Ans: dV = 0
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