11 mark
Which of the following is an example of a physical change?
Burning of wood
Fermentation of grapes
Melting of ice
Rusting of iron
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Chemical Changes (College Board AP® Chemistry)
Exam Questions
19 mins11 questions21 mark
What of the following is a key characteristic of a chemical change?
New substances with different properties are formed.
The appearance of the substance changes.
The mass of the substance changes.
The state of matter changes.
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31 mark
Aqueous Pb(NO3)2 reacts with aqueous KI to produce a solid precipitate of PbI2 and aqueous KNO3.
Which of the following is the balanced net ionic equation for the reaction described above?
K+ (aq) + NO3- (aq) → KNO3(aq)
Pb(NO3)2 (aq) + 2I- (aq) → PbI2 (s) + 2NO3- (aq)
Pb2+ (aq) + I- (aq) → PbI2 (s)
Pb2+ (aq) + 2I- (aq) → PbI2 (s)
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41 mark
The diagram above shows a reaction between carbon monoxide and oxygen.
Which of the following equations best describes the reaction?
C (g) + 2O2 (g) → CO2 (g)
2CO (g) + O2 (g) → 2CO2 (g)
CO (g) + O2 (g) → CO2 (g)
6CO (g) + 5O2 (g) → 6CO2 (g) + 2O2 (g)
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51 mark
What is the balanced molecular equation when Na2CO3 (aq) is mixed with HCl (aq)?
Na2CO3 (aq) + 2HCl (aq) → 2NaCl (aq) + H2O (l) + CO2 (g)
Na2CO3 (aq) + HCl (aq) → Na2Cl (aq) + H2O (l) + CO2 (g)
2Na2CO3 (aq) + 2HCl (aq) → 2NaCl (aq) + H2O (l) + CO2 (g)
Na2CO3 (aq) + HCl (aq) → NaCl (aq) + H2O (l) + CO2 (g)
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61 mark
When the equation below is balanced, what is the mole ratio of CO2 to H2O?
C3H5OH + O2 → CO2 + H2O
1:1
1:2
2:1
3:2
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11 mark
Which of the following comparisons of chemical and physical processes is the most accurate?
Chemical and physical processes are characterized by changes in intramolecular forces.
Chemical and physical processes are characterized by changes only in intermolecular forces.
Chemical processes are characterized by changes in intramolecular forces, while physical processes are characterized by changes only in intermolecular forces.
Physical processes are characterized by changes in intramolecular forces, while chemical processes are characterized by changes only in intermolecular forces.
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21 mark
Which of the following best describes the change that takes place immediately after liquid ethanol is introduced into a previously evacuated vessel?
A chemical change takes place because covalent bonds are broken.
A chemical change takes place because intermolecular attractions are overcome.
A physical change takes place because covalent bonds are broken.
A physical change takes place because intermolecular attractions are overcome.
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31 mark
Which observation best shows that a chemical change occurs when a colorless liquid and a blue liquid are combined?
The resulting mixture was cloudy, and its temperature increased.
The total volume of the mixture was equal to the sum of the initial volumes, but the blue color faded slightly.
The resulting liquid was uniformly light blue, and no other changes were observed.
The liquids formed two separate layers in the beaker after being stirred.
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11 mark
When two clear aqueous solutions are mixed, the resulting mixture becomes slightly cloudy but does not form a stable solid precipitate. Gentle heating of the mixture restores its original clarity.
Which of the following statements best characterizes this observed change?
The cloudiness must represent a reversible chemical change, forming a precipitate that then dissolves upon heating.
The cloudiness indicates incomplete mixing and is purely physical since no reaction occurred.
The temporary cloudiness is a physical change since the original composition is restored by gentle heating.
The observed cloudiness must represent permanently formed new species, classifying it as a chemical change.
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