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Sch 2100 : Atomic Structure Question Paper
Sch 2100 : Atomic Structure
Course:Bachelor Of Science In Medical Microbiology
Institution: Jomo Kenyatta University Of Agriculture And Technology question papers
Exam Year:2012
JOMO KENYATTA UNIVERSITY
OF
AGRICULTURE AND TECHNOLOGY
University Examinations 2012/2013
FIRST YEAR FIRST SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE IN MEDICAL MICROBIOLOGY
SCH 2100 : ATOMIC STRUCTURE
DATE: AUGUST 2012 TIME: 2 HOURS
INSTRUCTIONS: ANSWER QUESTION ONE (COMPULSORY) AND
ANY OTHER TWO QUESTIONS.
______________________________________________________________________
DATA:
h - 6.63 x 10-34J.s
c - 3.0 x 108m/s
NA - 6.023 x 1023mol-1
RH - 2.18 x 10-18J
QUESTION ONE (30 MARKS)
(a) List three subatomic particles and their characteristics.
[1½ marks]
(b) Explain the meaning of the symbol . [1½ marks]
(c) (i) What is a periodic table? [1 mark]
(ii) Explain the general trend of atomic radii across the period
and down a group. [3 marks]
(iii) Using s, p. d notation, write the electronic configuration of an element with atomic number 34. Indicate the group and period that it belongs to. [3 marks]
(d) (i) Define the term mole. [1 mark]
(ii) Calculate the number of atoms in 6g of Cu. [2 marks]
(Cu = 63.6g)
(iii) Calculate the molar mass of a compound if 0.372 mole of it
has a mass of 152g. [2 marks]
(e) With examples, explain the meaning of the following:
(i) 1 Normal solution. [2 marks]
(ii) 1 Molar solution. [2 marks]
(iii) 1 Percent solution (W/W). [2 marks]
(f) (i) What is a wave? [1 mark]
(ii) Calculate the wavelength (in namometres) of light having a
frequency of 8.6 x 1013Hz. [2 marks]
(g) A sample of 0.322g of an ionic compound containing the bromide ion (Br-) is dissolved in water and treated with an excess of AgNO3. If the mass of the AgBr precipitate that forms is 0.696g, calculate the percent mass of Br in the original sample. [6 marks]
Ag = 108g; Br = 80g)
QUESTION TWO (20 MARKS)
(a) What is an emission spectra? [1 mark]
(b) Calculate the wavelength (in nm) of a photon emitted by a hydrogen atom when its electron drops from n = 5 to n = 3 state.
[3 marks]
(c) Explain what is an atomic orbital and how it differs from an orbit.
[2 marks]
(d) Calculate the volume (cm3) of a 0.500MHCl solution needed to neutralize each of the following:
(i) 10ml of a 0.300M NaOH solution. [2 marks]
(ii) 10ml of a 0.200M Ba(OH)2 solution. [3 marks]
(e) (i) Explain what is dilution as applied to aqueous solutions.
[1 mark]
(ii) A 46.2cm3 of 0.568M calcium nitrate (Ca(NO3)2) solution is
mixed with 80.5 cm3 of 1.396M calcium nitrate solution. Calculate the concentration of the final solution.
[4 marks]
(f) Balance the following equations: [4 marks]
(i) Ba(OH)2(aq) + H3PO4(aq)
(ii) HClO4(aq) + Mg(OH)2(s)
QUESTION THREE (20 MARKS)
(a) (i) What is meant by an empirical formula? [1 mark]
(ii) A sample of a compound containing boron (B) and hydrogen (H) contains 6.44g of B and 1.803 of H. The molar mass of the compound is about 30g. What is its molecular formula?
B = 10.81g; H = 1.00g [4 marks]
(b) Define each of the following:
(i) Limiting reagent. [1 mark]
(ii) Excess reagent. [1 marks]
(iii) Nitric oxide (NO) reacts with oxygen gas to form nitrogen dioxide (NO2) 2NO(g) + O2(ag) 2NO2(g)
In one experiment, 0.886 mole of NO is mixed with 0.503 mole of O2. Calculate which of the two reactants is the limiting reagent and the number of moles of NO2 produced.
[2 marks]
(c) A sample of a compound of Cl and O reacts with an excess of H2 to give 0.233g of HCl and 0.403g of H2O. Determine the empirical formula of the compound. [6 marks]
Cl = 35.5 g; 0 = 16g
(d) A 0.8870g of a mixture of NaCl and KCl is dissolved in water and the solution is then treated with an excess of AgNO3 to yield 1.913g of AgCl. Calculate the percent by mass of each compound in the mixture. [6 marks]
(Ag = 108g; Cl = 35.5g; Na = 23g; K = 39)
QUESTION FOUR (20 MARKS)
(a) When heated, lithium reacts with Nitrogen to form lithium nitrate:
6Li(s) + N2(g) 2Li3N(s)
(i) Calculate the theoretical yield of Li3N in grams when 12.3g of Li are heated with 33.6g of N2 (Li = 6.94g, N = 14).
(ii) If the actual yield of Li3N is 5.89g, calculated the percent yield of the reaction.
(b) Calculate the molarity of 6.57g of methanol (CH3OH) in 1500 ml of solution.
(c) Oxalic acid (H2C2O4) is present in many plants. If 24cm3 of 0.01M KMnO4 solution is needed to titrate 1.00g of a sample of H2C2O4 to the equivalence point, what is the percent by mass of H2C2O4 in the sample?
2MnO + 16H+ + 5C2O 2Mn2+10CO2 + 8H2O
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