Chemistry 1154 Fall 2016 Test 1
Thursday, September 29, 2016
Time: 1 hour 50 minutes
Name: _________________________
Student #: _________________________
This test consists of nine pages of questions, the formula sheet, and a periodic table. Please
ensure that you have a complete test and, if you do not, obtain one from me immediately.
There are 36 marks available. Good luck!
1) [2 marks] A 10.00 mL aliquot of H3PO4 required 15.00 mL of 0.2000 M NaOH to titrate:
3NaOH(aq) + H3PO4(aq)
Na3PO4(aq) + 3H2O(l)
What was the concentration of Na3PO4 after reaction? Give your answer in moles/L.
2) [3 marks] A 635.9-mg sample of a compound of formula M2CO3 (where “M” is some
mystery metal) was reacted with excess Al(NO3)3:
3M2CO3(aq) + 2Al(NO3)3(aq)
Al2(CO3)3(s) + 6MCl(aq)
A total of 468.0 mg of Al2(CO3)3 (234.0 g/mol) was collected. What is the metal, M?
3) [7 marks total] Penicillin is 11.516 percent nitrogen and 26.308 percent oxygen by mass.
Penicillin contains carbon, hydrogen, oxygen, nitrogen, and sulphur.
a) [4 marks] A 2432.6-mg sample of penicillin was burned, and 3960.9 mg of CO2
(44.01 g/mol) and 991.1 mg of H2O (18.02 g/mol) were collected. What is the empirical
formula of penicillin?
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b) [3 marks] Penicillin reacts with NaOH according to the (balanced) reaction:
Penicillin + NaOH
products
A 1216.3-mg sample of penicillin required 25.00 mL of 0.2000 M NaOH for complete
reaction. What is the molecular formula of penicillin?
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4) [4 marks] A 258.6-mg sample of impure iron was reacted with 10.00 mL of 6.000 M HNO3:
6HNO3(aq) + Fe(s)
3NO2(g) + Fe(NO3)3(aq) + 3H2O(l)
The resulting solution was made up to the 200.0-mL mark, and a 15.00-mL aliquot taken
and the excess HNO3 titrated with 27.00 mL of 0.1000 M NaOH:
NaOH(aq) + HNO3(aq)
NaNO3(aq) + H2O(l)
What was the percent purity of the original sample? (Assume any impurities present are
unreactive.)
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5) [4 marks] A 1631.37-mg sample of a mixture of copper and silver was reacted with excess
HNO3:
2HNO3(aq) + Ag(s)
4HNO3(aq) + Cu(s)
NO2(g) + AgNO3(aq) + H2O(l)
2NO2(g) + Cu(NO3)2 + 2H2O(l)
The NO2 was collected in a 60.0-L flask, where its pressure was determined to be
10.33 mbar at 25.03°C. What was the mass percent of Cu in the original mixture?
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6) [4 marks] If 2123.75 mg of 80.00 % pure AgNO3 (169.9 g/mol) are mixed with 416.0 mg of
75.00% pure Na2S (78.0 g/mol):
2AgNO3(aq) + Na2S(aq)
Ag2S(s) + 2NaNO3(aq)
how many mg of Ag2S (247.8 g/mol) should be collected? Assume the reaction occurs with
a 90.00 percent yield.
7) [2 marks] Concentrated HCl (36.46 g/mol) is 38.0 percent HCl by mass. Its density is
1.1885 g/mL. What is the concentration of HCl in moles/L in this solution?
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8) [4 marks] When 1883.25 mg of a compound of formula MNO3 (“M” is a mystery element) is
mixed with excess Na3PO4, 1428.04 mg of M3PO4 are collected:
3MNO3(aq) + Na3PO4(aq)
M3PO4(s) + 3NaNO3
What is the metal, M?
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9) [3 marks] The density of gaseous XF3 (where X is some unknown element) at 27.36°C and
2 bars of pressure is 60.0 percent of the density of gaseous XF5 at 19.42°C and 2.3 bars of
pressure. What is the element, X?
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10) [3 marks] The molar mass of “unknown metal M” was determined in exactly the same way
as the molar mass of magnesium (that we discussed in class). In this case, the metal reacts
with HCl according to the reaction:
2M(s) + 2HCl(aq)
2MCl(aq) + H2(g)
The following data were collected:
Data (units)
Mass of M (mg)
Vgas (mL)
Patm (torr)
Tsol’n (°C)
VPsol’n (torr)
hsol’n (mm)
Dsol’n (kg/m3)
value
149.8
41.5
762.3
20.6
18.2
118.5
1000.
What is the metal, M?
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