STRUCTURE QUESTIONS

1. The following table shows the relative atomic mass of a few types of carbon.

Substance Relative atomic

mass Carbon-12 12.000

Carbon-13 13.0003

Graphite 12.011

Diamond 12.011

iv. How do the structures of diamond and graphite explain their electrical conductivities

respectively?

v. The reaction C(diamond) � C(graphite) ; ∆H = -3 kJ / mol is exothermic. Explain why this reaction

does not occur spontaneously. [8]

(b) Carbon-14 can be formed by the reaction between cosmic rays and nitrogen in the atmosphere.

i. What are cosmic particles?

ii. Write a balanced equation for the above reaction. [2]

(a) i. Explain why carbon-12 replaced oxygen as a

standard in the determination of relative

atomic mass.

ii. Why does the relative atomic mass of diamond

differ from that of carbon-12?

iii. Calculate the percentage of 12C in graphite.

2. Beams of particles travelling at the same speed from different sources are subjected to an electric

field as shown in the diagram below. A beam of neutrons has already been drawn

(a) Sketch and label on the diagram above how beams of each of the following particles are

affected by the electric field:

(i) protons (ii) electrons (iii) 2H+ [3]

(b) Explain briefly the position and shape of each beam.

(i) protons (ii) electrons (iii) 2H+ [3]

3. (a) Describe the relative charges and masses of the three types of particles containing within the atom.

How do beams of these particles behave in an electric field? [6]

(b) Because of differing proportions of isotopes, the relative mass of lead depends on its source. Two

samples of lead were subjected to analysis. The mass spectrum of the first sample was taken and the

following results were obtained

m/e value 204 206 207 208

relative abundance 27 48.0 41.5 100.0

When 1.00 g of the second sample was converted into lead (II) chloride, the mass of the product was

1.341g. Calculate the average relative atomic mass of each sample of lead, and decide whether or

not the two samples have identical isotopic compositions. [Take the relative atomic mass of chlorine

to be 35.45] [4]

4. The mass spectrum of naturally occurring magnesium is given below

24 25 26 m/e

(a) Name the ions that are responsible for the peaks

at positions 24, 25, dan 26 respectively.

(b) Calculate the relative abundance of each

isotope.

(c) Calculate the relative atomic mass of

magnesium. [6]

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PPU 962 Chemistry

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PPU 962 Chemistry: SEM 1, Chapter 1 = Atoms, Molecules and Stoichiometry

This document is not under copyrights of LRT Documents. The questions above is not printed question.

5. Compound, X, containing only carbon, hydrogen, and oxygen, has the empirical formula C3H6O.

The mass spectrum of X is given below.

14 15 26 27 42 43 58 m/e

(a) What is the molecular formula of X? Explain your

answer. [2]

(b) Identify the ionic species responsible for peaks

at relative masses 15 and 43. What is the

structural formula of X? [3]

(c) For each of the other lines, identify the ions that

are responsible for their occurrence. [5]

6. The diagram below shows one type of mass spectrometer

(a) Identify the functions or processes that occur in each part

labelled A to F. A mixture of 2H2 and 81Br2 was analysed by

using the spectrometer. The pattern of lines caused by ions

with single charges was obtained as follows [6]

(b) State the ions that caused each of the following lines. 2,

4, 81, 83, and 162 [3]

(c) What is the nucleon number registered on the scale of

that instrument if the heaviest ion obtained a second

charge? [1]

7. The diagram below shows ionic distances in a mass spectrometer using bromine gas. (Bromine has a

relative atomic mass of 79.91 and it contains two isotopes with nucleon numbers of 79 and 81)

Each of the groups of lines A, B, and C was produced by one of these ions : Br+ (g), Br2+ (g), and

Br2+(g). State which ion produces the lines in Group A Group B Group C

Identify each line in Groups B and C, and label the line in each group that has the highest intensity.

PPU 962 Chemistry

2 of 2

PPU 962 Chemistry: SEM 1, Chapter 1 = Atoms, Molecules and Stoichiometry

This document is not under copyrights of LRT Documents. The questions above is printed question.