2022
AP
®
Chemistry
Sample Student Responses
and Scoring Commentary
Inside:
Free-Response Question 7
•
•
•
• Scoring Guidelines
• Student Samples
• Scoring Commentary
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Question 7: Short Answer 4 points
(a) For the correct answer:
2
sp
1 point
(b)(i) For the correct answer:
+ 2 2−
K = [Ag ] [C O ]
sp 24
1 point
(ii)
For the correct calculated value:
−12
2
5.40 × 10 = 2
s s
( ) ( )
−12 3
5.40 × 10 = 4
s
−4
s
= 1.11 × 10
M
1 point
(iii) For a correct equation (state symbols not required):
Accept one of the following:
•
2− + −
() + HO() () +CO aq aq → HC O aq H O() l
24 3 24 2
•
2− + −
CO () + H() aq → HCO ()aq aq
24 24
•
2− +
CO aq aq → HCO() () + 2 HO () aq
24 3 224
+ 2 H O() l
2
AP® Chemistry 2022 Scoring Guidelines
•
CO
2−
() aq + 2 H
+
24
() aq → H
2
C
24
O() aq
1 point
Total for part (b) 3 points
Total for question 7 4 points
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Sample 7A 1 of 1
Sample 7B 1 of 1
Sample 7C 1 of 1
AP
®
Chemistry 2022 Scoring Commentary
Question 7
Note: Student samples are quoted verbatim and may contain spelling and grammatical errors.
Overview
Question 7 prompted students to analyze solubility properties of Ag
2
C
2
O
4
.
Part (a) asked the students to identify the hybridization of either carbon atom in the oxalate ion
(Learning Objective SAP-4.C, Science Practice 1.A from the AP Chemistry Course and Exam
Description).
Part
(b) offered students
the opportunity to earn 3
points.
For
part
(b)(i), the students were asked to
write the K
sp
expression for the dissolution of Ag
2
C
2
O
4
(SPQ-5.A, 5.B). Based on the equilibrium
expression, part (b)(ii) had the students calculate the molar solubility of Ag
2
C
2
O
4
given
the K
sp
value (SPQ-5.A, 5.F). Part (b)(iii) asked students to write the net-ionic equation that
explained why the solubility of Ag
2
C
2
O
4
increased after the addition of a strong acid to the solution
(SPQ-5.C, 6.D).
Sample: 7A
Score: 4
This response earned 4 points
. In part
(a) the point was earned for the correct hybridization.
In part (b)(i) the point was earned for the correct K
sp
expression with the correct ions. In part (b)(ii)
the point was earned for the correct setup, correct values in the setup, and answer. In part (b)(iii) the
point was earned for a correct net-ionic equation.
Sample: 7B
Score: 3
This response earned 3 points. In part (a) the point was earned for the correct hybridization.
In part (b)(i) no point was earned because the K
sp
expression has the solid in the denominator.
In part (b)(ii) the point was earned for the correct setup, correct values in the setup, and correct
answer. In part (b)(iii) the point was earned for a correct net-ionic equation.
Sample: 7C
Score: 2
This r
esponse earned 2 points.
In part (a) the point was earned for the correct hybridization.
In part (b)(i) no point was earned because the concentration of silver ion is not squared. In part (b)(ii)
the point was earned because the answer is consistent with the K
sp
expression in part (b)(i).
In part (b)(iii) no point was earned because the net-ionic equation is incorrect; all reactants must
be ions.
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