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Dce0016:Chemistry Question Paper
Dce0016:Chemistry
Course:Diploma In Civil Engineering
Institution: Meru University Of Science And Technology question papers
Exam Year:2012
1
a) Given that the value of the principal quantum number n=3, what are the values of
i. Azimuthal quantum number , l and (1 ½ Marks)
ii. Magnetic quantum number, m? (3 ½ Marks)
b) Draw the shapes of
i. p- orbitals (3 Marks)
ii. d- orbitals (2 Marks)
c) i) The electron in hydrogen atom makes transition form ??1 = 1 to ??2 = 4. Calculate the
energy change ???, given that ?? = 2.18 × 10-18??. (5 Marks)
ii) The Balmer series portion of the hydrogen spectrum is given by the expressions
1
?
= ????
1
22 -
1
??2
Given that ???? = 1.09678 × 10+7??-1, ?? = 3.0 × 108????-1. Calculate the wavelength
of a radiation emitted by an electron falling from ?? = 5 in the Balmer series.
(5 Marks)
d) An element has 31 protons in its nucleus
i. Write the electronic configuration of the element using the inert gas core.
(2 Marks)
ii. In which group does the element belong? Explain your answer (3 Marks)
e) Show the Lewis structures of the following chemical species.
i. NaCl (2 Marks)
ii. ????4
+ (2 Marks)
2
iii. Draw the structures of water molecule and indicate electric charges associated
with it. (1 Mark)
QUESTION TWO (15 MARKS)
A compound contains carbon and hydrogen only and is 85.6% carbon and 14.4% hydrogen by
weight.
a) Determine the empirical formula of the compound. (6 Marks)
b) 10g of the same compound occupy 5.322L at STP.
i. How many moles of the compound is represented by the 5.322L? (molar volume
= 22.4L at STP) (3 Marks)
ii. From your answer in b(i) above, determine the molecular formula of the gaseous
hydrocarbon/compound. (6 Marks)
QUESTION THREE (15 MARKS)
a) Describe with aid of a diagram the fundamental difference between JJ Thomson and
Rutherford’s models of the atom. (6 Marks)
b) The charge on an electron is -1.602 × 10-19 coulombs. Given that
??
??
of a proton is
9.575 × 104 coulombs/gram, calculate the mass of a proton in kilograms.(4 Marks)
c) i) Give an outline of fundamental differences between a continuous spectra and a line
spectra. (3 Marks)
ii) What is the practical application of atomic line spectra? (2 Marks)
QUESTION FOUR (15 MARKS)
a) Give the electronic structure of the following chemical species;- [F=9, Mg=12, P=15]
i. ??-
ii. ????2+
iii. ??
iv. Which ones of the species are electronic. (4 Marks)
b) Using elements, chlorine and sodium, explain the difference between ionic and covalent
bonding in chemical substances. [Cl=17, Na=11]. (4 Marks)
c) Oxygen atom belongs to the group VI A of the periodic table of elements. Oxygen
combines with hydrogen to form water
i. Write a balanced chemical equation to show the formation of water from oxygen
and hydrogen. (2 Marks)
3
ii. Write an electronic configuration of oxygen and hence draw the orbital diagram
(2 Marks)
iii. Draw the Lewis structure for the water molecule indicating all the bonding and
non bonding pairs. (3 Marks)
QUESTION FIVE (15 MARKS)
a) State the Avogadro’s law. (2Marks)
b) Calculate the volume occupied by 0.1kg of carbon monoxide at a temperature of 7000C
and a pressure of 0.1 atmospheres. [C=12.00, O=16.00, R=0.082L atmMol-1K-1].
(5 Marks)
c) The concentration of a given solution of hydrochloric acid HCl is given as 0.05m.
Calculate the pH of this solution. (3 Marks)
d) Given that the standard enthalpies of formation of CO2(g) is = -393.5??????????-1 and that
of ??2??(g) is -285.8??????????-1 and that the standard enthalpy change for the reaction of
ethyne (C2H2) is as shown
2C2H2(g) +5O2(g) 4CO2(g) + 2H2O(l);??? = -2598.8??????????-1. Calculate
the standard enthalpy of formation of ethyne (C2H2) from its elements:
2C(graphite) + H2(g) C2H2(g) ??? =? (5 Marks)
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