IB
Chemistry
Question Bank
Free International Baccalaureate Diploma Programme Exam Style Questions
Delve into the realm of International Baccalaureate Chemistry with our collection of free IB past paper questions. Test your knowledge across various Chemistry topics, enhancing your understanding and preparing you for the IB examinations.
Question 1
2.00 mol of a hydrocarbon with an empirical formula of $\mathrm { C } \mathrm { H } _ { 2 }$ has a mass of 140 g. What is the molecular formula of this compound?
[ 1 ]
A.
$\mathrm { C } _ { 2 } \mathrm { H } _ { 4 }$
B.
$\mathrm { C } _ { 3 } \mathrm { H } _ { 6 }$
C.
$\mathrm { C } _ { 4 } \mathrm { H } _ { 8 }$
D.
$\mathrm { C } _ { 5 } \mathrm { H } _ { 10 }$
Rationale
M = m / n = 140 g / 2 mol = 70 g mol-1
Mr of $\mathrm { C } _ { 5 } \mathrm { H } _ { 10 }$ $\approx$ 70.1, so this is the correct answer
Question 2
In which mixture is Mg(OH)2 in excess?
[ 1 ]
A.
0.10 mol Mg(OH)2 + 0.20 mol H2SO4
B.
0.10 mol Mg(OH)2 + 0.10 mol H2SO4
C.
0.20 mol Mg(OH)2 + 0.20 mol HNO3
D.
0.10 mol Mg(OH)2 + 0.20 mol HNO3
Rationale
Molar ratio of Mg(OH)2 to H2SO4 is 1:1
Molar ratio of Mg(OH)2 to HNO3 is 1:2
Thus, C is the only answer where Mg(OH)2 is in excess
Question 3
$5~ \mathrm { dm } ^ { 3 }$ of carbon monoxide, CO(g), and 3 dm3 of oxygen, O2(g), at the same temperature and pressure are mixed together. Assuming complete reaction according to the equation given, what is the maximum volume of carbon dioxide, $\mathrm { CO } _ { 2 } \left( \mathrm {g} \right)$, in $\mathrm { dm } ^ { 3 }$, that can be formed?
$$ 2 \mathrm { CO } ( \mathrm { g } ) + \mathrm { O } _ { 2 } ( \mathrm {~g} ) \rightarrow 2 \mathrm { CO } _ { 2 } ( \mathrm {g} ) $$
[ 1 ]
A.
5
B.
6
C.
8
D.
10
Rationale
O2: 3 dm3
CO: 5 / 2 = 2.5 dm3
So CO is the limiting reactant
To find CO2 produced, use molar ratios: 5 dm3 x 1 = 5 dm3
Remember, you don't need to convert to moles if all reactants and products are gaseous due to ideal gas laws.
Question 4
In the emission spectrum of the hydrogen atom, which electronic transition would produce a line in the visible region of the electromagnetic spectrum?
[ 1 ]
A.
$n = 5 \to n = 3$
B.
$n = 3 \to n = 1$
C.
$n = 3 \to n = 2$
D.
$n = 10 \to n = 1$
Rationale
Transitions to n = 2 produce visible light
Question 5
What is the total number of valence electrons in NH4+?
[ 1 ]
A.
5
B.
8
C.
9
D.
10
Rationale
N has 5 ve-
H has 1
Total would be 9, but due to the + charge it is 8
Question 6
Which statement about the number of protons, electrons and neutrons in an atom is always correct?
[ 1 ]
A.
The relative atomic mass minus the number of neutrons equals the number of electrons
B.
The number of protons plus the number of electrons equals the number of neutrons
C.
The number of neutrons is always the same
D.
The number of neutrons equals the number of electrons
Rationale
The number of electrons and protons are the same in an atom (uncharged)
So RAM minus neutrons equals protons/electrons
Question 7
What is the composition protons, neutrons and electrons of 69Ga3+ ?
| Protons | Neutrons | Electrons | |
|---|---|---|---|
| A | 31 | 69 | 31 |
| B | 38 | 69 | 28 |
| C | 31 | 39 | 28 |
| D | 38 | 39 | 31 |
[ 1 ]
A.
A
B.
B
C.
C
D.
D
Rationale
69 is the atomic mass, 31 is the atomic number
69 - 31 = 39 is the number of neutrons
Electrons: 31 - 3 = 28
Question 8
Which electronic transition emits radiation of the highest energy?
[ 1 ]
[© Abaccus Ltd 2022]
A.
A
B.
B
C.
C
D.
D
Rationale
The transition down to n = 1 emit the highest energy radiation (UV light)
Question NaN
2.00 mol of a hydrocarbon with an empirical formula of $\mathrm { C } \mathrm { H } _ { 2 }$ has a mass of 140 g. What is the molecular formula of this compound?
[ 1 ]
A.
$\mathrm { C } _ { 2 } \mathrm { H } _ { 4 }$
B.
$\mathrm { C } _ { 3 } \mathrm { H } _ { 6 }$
C.
$\mathrm { C } _ { 4 } \mathrm { H } _ { 8 }$
D.
$\mathrm { C } _ { 5 } \mathrm { H } _ { 10 }$
Rationale
M = m / n = 140 g / 2 mol = 70 g mol-1
Mr of $\mathrm { C } _ { 5 } \mathrm { H } _ { 10 }$ $\approx$ 70.1, so this is the correct answer
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