Name: ________________________
honors Chem
date: ___________
Weekly quiz: significant figures, conversion factor, dimensional analysis, denisty [10 points]
Show your work in an organized manner, include (i) any relevant equation (or formula), (ii) conversion
factor(s), (iii) put the proper units in your calculations and answer, and (iv) have the proper number of
significant figures in your answer.
1.
Solve [2 points]
a.
22.0 / 7.0 = _3.1442  3.1_______
b.
131.25 + 36.839 = _168.089  168.09___
Solve: 275 mm2 = __ m2 [2 points]
2.
𝑚
2
275 𝑚𝑚2 ( 3
) = 275 𝑚𝑚2
10 𝑚𝑚
3.
𝑉=
𝑑=
𝑚2
106 𝑚𝑚2
= 275 ∗ 10− 6 𝑚2
Based on the following information data, determine the density (in g / mL) of a 75 kg sphere
4
with a radius of 25.0 cm. [hint: surface area of a sphere = 4 π r2;volume of a sphere = π r3; 6
3
points]
4
4
𝜋 𝑟 3 = 𝜋 (25 𝑚𝑚)3 = 65449.9 𝑐𝑚3
3
3
𝑚
𝑉
=
75 𝑘𝑔
65449.9 𝑐𝑚
∗
3
𝑐𝑚3
𝑚𝐿
∗
103 𝑔
𝑘𝑔
=
1.1 𝑔
𝑚𝐿
Name: ________________________
AP Chem
date: ___________
Weekly quiz: solution stochiometry [10 points]
Show your work in an organized manner, include (i) any relevant equation (or formula), (ii) conversion
factor(s), (iii) put the proper units in your calculations and answer, and (iv) have the proper number of
significant figures in your answer.
1.
Mix aqueous solutions of 25.0 mL of 35.0 mM calcium nitrate and 15.0 mL of 45 mM sodium
phosphate.
a.
Write the balanced chemical equation describing this reaction [3 points]
3 Ca(NO3)2 + 2 Na3PO4  6 NaNO3 + Ca3(PO4)2
b.
Identify the limiting reactant; justify. [4 points]
 #mole {Ca(NO3)2} = [Ca(NO3)2 ] VCa(NO3)2 = 25 mL*35 mM = 0.875 mmole
#mole {Na3PO4} = [Na3PO4] V Na3PO4 = 15 mL * 45 mM = 0.675 mmole
 # mole Ca(NO3)2 (need to react with 0.675 mmole Na3PO4)
= 0.675 𝑚𝑚𝑜𝑙𝑒 𝑁𝑎3 𝑃𝑂4 ∗
3 𝑚𝑚𝑜𝑙𝑒 𝐶𝑎(𝑁𝑂3 )2
2 𝑚𝑚𝑜𝑙𝑒 𝑁𝑎3 𝑃𝑂4
= 1.023 𝑚𝑚𝑜𝑙𝑒 𝐶𝑎(𝑁𝑂3 )2
 as # mole Ca(NO3)2 present < # mole Ca(NO3)2 needed to react with Na3PO4,
Ca(NO3)2 is the limiting reactant
c.
Determine the # of grams of the precipitate in the reaction. [3 points]
# g Ca(NO3)2
= 0.875 𝑚𝑚𝑜𝑙𝑒 𝐶𝑎(𝑁𝑂3 )2 ∗
= 0.0904 g
1 𝑚𝑚𝑜𝑙 𝐶𝑎3 (𝑃𝑂4 )2
𝑚𝑜𝑙
310 𝑔 𝐶𝑎3 (𝑃𝑂4 )2
∗
∗
3
3 𝑚𝑚𝑜𝑙𝑒 𝐶𝑎(𝑁𝑂3 )2 10 𝑚𝑚𝑜𝑙
𝑚𝑜𝑙 𝐶𝑎3 (𝑃𝑂4 )2