PPU 962 Chemistry
PPU 962 Chemistry: SEM 1, Chapter 1 = Atoms, Molecules and Stoichiometry
STRUCTURE QUESTIONS 1.
The following table shows the relative atomic mass of a few types of carbon. carb on. Substance
Relative atomic
Carbon-12
12.000
Carbon-13 Graphite Diamond
13.0003 12.011 12.011
iv. iv.
(a) (a) i.
ii. iiiii.i.
Explain why carbon-12 replaced oxyge ox yge n as a sta nda rd in the determinatio determination n of relative atomic mass. Why does the rela tive atomic mass mass of diamond diamond differ from that of carbon-12? carbon-12? Calculate Calcula te the percentage percen tage of 12 C in graphite.
How do the structures of dia mon d an d gra ph ite expl ai n their electrical conductivities respectively? The reaction C(diamond) C(graphite) ; H = -3 kJ / mol is exothermic. Explain why this reaction does not occur spontaneously. [8]
v.
(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]
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 Sketch and label on the diagram diagram above how beams of each of the following following par tic les a re affected by the electric field: (i) protons (ii) electrons (iii) 2H+ Explain briefly the position and shape of each beam. (i) protons (ii) electrons (iii) (iii) 2H+
(b)
3. (a) (b)
[3] [3]
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] 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 (a) 8
(b) (c)
24
1 of 2
1
1
25
26
Name the ions that are responsible for the peaks at positions 24, 25, dan 26 respectively. Calculate the relative abundance of each isotope. Calculate the relative atomic mass of magnesium. [6]
m/e
This document is not under copyrights of LRT Documents. The questions above is not printed question.
PPU 962 Chemistry
PPU 962 Chemistry: SEM 1, Chapter 1 = Atoms, Molecules and Stoichiometry
5. Compound, Compound, X, cont co ntain ain ing only ca rbo n, hydrogen, hydrogen, and oxygen, oxygen, has the empirical empirical formula formula C3H6O. The mass spectrum of X is given below. (a) (b)
(c)
14 15
6.
26 27
42 43
58
m/e
The diagram below shows one type of mass spectrometer (a)
7.
What is the molecular formula of X? Explain your answer. [2] Identify the ionic species responsible for peaks at relative masses 15 and 43. What is the structural formula of X? [3] For each of the other lines, identify the ions that are responsible for their occurrence. [5]
Identify the functions or processes that occur in each part labelled A to F. A mixture of 2H2 and 81Br 2 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]
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), Br 2+ (g), and Br 2+(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.
2 of 2
This document is not under copyrights of LRT Documents. The questions above is printed question.
