Sign In

Essential Chemistry for IGCSE - Chemical Calculations (Section 6)

1
What is the unit of concentration?
Answer
(B)
mol/dm³
2
Which factors will affect the accuracy of a titration?
Answer
C
D
3
How can you determine the molecular formula of a compound, given the empirical formula?
Answer
(C)
By knowing the relative formula mass.
4
How can you convert cm³ to dm³?
Answer
(B)
Divide by 1000
5
What type of formula shows the simplest whole number ratio of atoms?
Answer
(B)
Empirical formula
6
How is solution concentration usually expressed?
Answer
(C)
mol/dm³
7
What is the formula used for calculating the concentration of a solution?
Answer
(A)
moles / volume (dm³)
8
If the theoretical yield is 20g and the actual yield is 16g, what is the percentage yield?
Answer
(A)
80%
9
What is the relationship between mass and moles, that can be used in solution concentration calculations?
Answer
(B)
Moles = Mass / Molar Mass
10
If the actual yield is 5 g and the theoretical yield is 20 g, what is the percentage yield?
Answer
(B)
25%
11
What is the unit for relative atomic mass?
Answer
(B)
amu
12
Which value does the 'relative atomic mass' represent?
Answer
(B)
The average mass of the isotopes of an element compared to carbon-12.
13
What is the visual cue that indicates the endpoint in a titration?
Answer
(C)
A change in the color of the indicator
14
A reaction's theoretical yield is 100 g. The actual yield from the experiment is 75 g. What is the percentage yield?
Answer
(B)
75%
15
What is the amount of a substance that contains 6.022 x 10^23 particles called?
Answer
(B)
A mole
16
What is the first step in calculating the concentration of a solution in mol/dm³?
Answer
(A)
Calculate the number of moles of solute.
17
Which factor(s) can prevent a chemical reaction from reaching 100% yield?
Answer
A
B
C
18
What is the definition of an alkali in summary question 1?
Answer
(B)
A base that is soluble in water.
19
What does percentage yield measure?
Answer
(B)
The efficiency of a reaction.
20
What is the correct formula for converting grams to moles?
Answer
(B)
Moles = Mass / Molar mass
21
What is the limiting reactant in a chemical reaction?
Answer
(A)
The reactant that is used up first.
22
How do impurities affect the purity of a chemical?
Answer
(C)
They decrease the purity.
23
Which of the following are advantages of titrations?
Answer
A
B
C
24
Which of the following statements correctly defines the limiting reactant?
Answer
(B)
The reactant that is used up completely.
25
What are the basic steps when finding the empirical formula?
Answer
A
B
D
26
If you obtain 10.0 g of product, but the theoretical yield was 12.0 g, what is the percentage yield?
Answer
(A)
83.3%
27
Which of the following decreases the yield of a reaction?
Answer
C
D
28
If the empirical formula of a compound is CH and the relative formula mass is 26, what is the molecular formula?
Answer
(C)
C₂H₂
29
What are the units of solution concentration commonly expressed in?
Answer
(C)
mol/dm³
30
What is the purpose of calculating percentage purity?
Answer
(B)
To quantify the amount of a desired compound within a sample.
31
What is the molar volume of a gas at room temperature and pressure?
Answer
(B)
24 dm³/mol
32
In the context of summary question 1, what phrase is missing?
Answer
(C)
formula
33
What volume does 1 mole of a gas occupy at room temperature and pressure (RTP)?
Answer
(B)
24 dm³
34
Which of the following will reduce the percentage yield of a reaction?
Answer
A
B
35
If you have 48 dm³ of a gas at RTP, how many moles of gas do you have?
Answer
(B)
2 mol
36
The purity of a chemical sample is affected by:
Answer
A
B
37
What is the purpose of an indicator in a titration?
Answer
(B)
To show when the reaction is complete.
38
Which of the following would not affect the percentage purity of a substance?
Answer
(C)
Loss of product in transfer.
39
What does the molecular formula show?
Answer
(B)
The actual number of atoms in a molecule.
40
In a chemical reaction, which factor typically determines the theoretical yield of a product?
Answer
(B)
The limiting reactant.
41
What does the molecular formula show?
Answer
(B)
The actual number of atoms in a molecule.
42
Which of the following items is required for an acid-alkali titration?
Answer
A
B
C
43
What tool is used to determine relative formula mass?
Answer
(B)
A mass spectrometer.
44
What is the molar mass of water (H2O)? (H = 1, O = 16)
Answer
(B)
18 g/mol
45
How is the limiting reactant determined?
Answer
(B)
The reactant that is completely consumed.
46
What is the effect of an impurity on a sample?
Answer
(B)
Decreases the purity
47
In a titration experiment, which of the following measurements are crucial for calculating the concentration of the unknown solution?
Answer
A
B
D
48
If a reaction gives a lower yield than expected, what is this primarily due to?
Answer
(B)
Side reactions occurring
49
If you have 117 grams of sodium chloride (NaCl), how many moles do you have? (Na=23, Cl=35.5)
Answer
(B)
1.0 moles
50
Which factor(s) can affect the percentage yield?
Answer
A
B
C