CHEM*1300 (F 2003)
1.
Fe2O3
(b)
ammonium carbonate
(b)
H2CO3
AgNO3
N2O5
(a)
The balanced equation is:
(b)
If there are 5.0 moles of PH3(g) available,
(i)
the number of moles of O2(g) needed to react completely is:
Al2(SO4)3
(c)
(d)
moles
the maximum number of moles of P2O5(s) and H2O(R) that can be obtained is:
P2O5(s):
moles
H2O(R):
moles
If the reaction proceeds with 80% yield, the number of moles
of PH3(g) required to prepare 4.0 moles of P2O5(s) is:
moles
When 5.0 moles of PH3(g) is mixed with 8.0 moles of O2(g),
the maximum number of moles of P2O5(s) and H2O(R) can be produced is:
P2O5(s):
moles
H2O(R):
moles
Nitric acid, HNO3(aq), is produced commercially by Ostwald process via the following sequence of reactions:
ÿ
4 NO(g) + 6 H2O(g)
Step (i):
4 NH3(g) + 5 O2(g)
ÿ
2 NO2(g)
Step (ii):
2 NO(g) + O2(g)
ÿ
2 HNO3(aq) + NO(g)
Step (iii): 3 NO2(g) + H2O(R)
(a)
(b)
6.
CFCl3
Phosphine, PH3(g), burns in oxygen to produce phosphorus pentoxide, P2O5(s) and water.
PH3(g) + O2(g) ÿ P2O5(s) + H2O(R)
(ii)
5.
potassium phosphate
Circle the substances listed below which are not ionic compounds:
K2Cr2O7
4.
SF4
Write chemical formulae corresponding to the following names:
(a)
3.
PAGE - 1
Name the following compounds:
(a)
2.
PROBLEM LAB FOR MIDTERM (I)
Assume 100% efficient in all three steps,
the number of moles of HNO3(aq) that can be produced from
12.0 moles of NH3(g) and excess O2(g) is:
moles
If Step (i) proceeds with 75% yield, Steps (ii) and (iii) with 100%,
then the number of moles of NH3(g) required to prepare
4.0 moles of HNO3(aq) is:
moles
Traumatic acid, a wound hormone found in plant, contains only C (12.01 g mol!1), H (1.01 g mol!1) and O
(16.00 g mol!1). When a 3.00 g sample of traumatic acid is burned in air, 6.94 g of CO2(g) and 2.38 g of
H2O(R) are formed.
(a)
The masses of carbon, hydrogen and oxygen in the sample are:
C:
g
H:
g
O:
(b)
The empirical formula of traumatic acid is:
(c)
If traumatic acid has an approximate molar mass of 228.3 g mol!1,
then the molecular formula is:
(d)
The balanced equation for the complete combustion of traumatic acid is:
(e)
The standard enthalpy of combustion of traumatic acid is !7.85 MJ mol!1.
When 10.0 g of traumatic acid is burned, the heat evolved is:
(f)
The mass of CO2(g) produced per 500.0 kJ of heat released is:
g
CHEM*1300 (F 2003)
PROBLEM LAB FOR MIDTERM (I)
7.
Write the net ionic equation for the reaction:
8.
Cadmium (112.4 g mol!1) is a very toxic cumulative poison with no known biological function as trace
minerals. The maximum acceptable concentration of cadmium in drinking water is 5.0 ppb.
(a)
Mg(OH)2(aq) + CO2(g)
PAGE - 2
The concentration of cadmium in:
MgCO3(s) + H2O(R)
ÿ
ppm
L
(b)
(c)
9.
10.
11.
mol
!1
Assuming an intake of 2.0 L of drinking water per day,
the maximum daily intake of cadmium from drinking water is:
µg
The concentration of 8.0 mL of 5.0 ppb Cd2+ solution diluted
to 400.0 mL total volume is:
ppb
15.3 g of cadmium nitrate (Cd(NO3)2, 236.3 g mol!1) is dissolved in 360 mL pure water.
mol L!1;
(a)
The concentration of Cd(NO3)2:
(b)
The concentration of nitrate ion (62.0 g mol!1) is:
(c)
The number of atoms of oxygen is::
(d)
The volume of this solution required to prepare exactly
500.0 mL of 0.054 mol L!1 Cd2+ solution is:
mol L!1
Cd2+:
mol L!1;
ppm
atoms
mL
A 2.86 g sample of impure MgSO4•7H2O (246.5 g mol!1) was found to contain 31.12% water (18.02 g mol!1).
(a)
the number of moles of water in the sample is:
(b)
the mass of magnesium (24.31 g mol!1) in the sample is:
(c)
the percent of MgSO4•7H2O in the impure sample is:
4.56 g of solid ZnCl2 (136.3 g mol!1) is dissolved in 200 mL of water and then added to a solution of 300 mL
of 0.125 M NaOH, a white precipitate of zinc hydroxide (99.4 g mol!1) and sodium chloride are formed.
(a)
Write a balanced net ionic equation for the precipitation reaction.
(b)
The mass required to prepare 300 mL of 0.125 M NaOH (40.0 g mol!1) is:
(c)
The limiting reagent of this reaction is:
(d)
The maximum mass of zinc hydroxide produced is:
(e)
The concentration of sodium chloride in the final solution is:
(f)
The mass of each reactant leftover is:
g
ZnCl2:
(g)
g
mol L!1
NaOH:
If 1.58 g of zinc hydroxide is obtained, then the percent yield is:
12.
The thermochemical equation to define the standard molar enthalpy of formation of mercury (II) thiocyanate,
∆Hof [Hg(SCN)2(s)], is:
13.
Circle the compounds listed below which have the molar enthalpy of formation = 0 at 298 K and 1 atm.
Br2(R)
14.
CO2(g)
I2(g)
H2O(R)
K(s)
Given the following three combustion reactions:
S(s) + O2(g) ÿ SO2(g)
2 H2(g) + O2(g) ÿ 2 H2O(R)
2 H2S(g) + 3 O2(g) ÿ 2 SO2(g) + 2 H2O(R)
The standard molar enthalpy of formation of H2S(g) is:
Cl(g)
∆Ho = !296 kJ
∆Ho = !572 kJ
∆Ho = !1124 kJ
O3(g)
H+(aq)
CHEM*1300 (F 2003)
PROBLEM LAB FOR MIDTERM (I)
PAGE - 3
Data Information
For Solids:
n(x) '
For Solutions:
m(x)
M(x)
(units:
g
)
g mol !1
c(x) '
ANSWERS
(a)
(b)
iron (III) oxide (or ferric oxide)
sulfur tetrafluoride
2.
(a)
(b)
(NH4)2CO3
K3PO4
3.
H2CO3; CFCl3; N2O5
4.
(a)
(b)
(c)
(d)
2 PH3(g) + 4 O2(g) ÿ P2O5(s) + 3 H2O(R)
(i)
10 mol O2(g)
(ii) 2.5 mol P2O5(s); 7.5 mol H2O(R)
10 mol PH3(g)
2.0 mol P2O5(s); 6.0 mol H2O(R)
5.
(a)
(b)
8.00 mol HNO3(aq)
8.0 mol NH3(g)
6.
(a)
(b)
(c)
(d)
(e)
(f)
C: 1.89 g; H: 0.267 g; O: 0.84 g
C3H5O
C12H20O4
C12H20O4(s) + 15 O2(g) ÿ 12 CO2(g) + 10 H2O(R)
!344 kJ (or !344 MJ)
33.6 g
7.
Mg2+(aq) + 2 OH!(aq) + CO2(g)
8.
(a)
(b)
(c)
5.0 × 10!3 ppm;
10 µg
0.10 ppb
9.
(a)
(b)
(c)
(d)
Cd(NO3)2: 0.180 mol L!1; Cd2+: 0.180 mol L!1
0.360 mol L!1; 2.23 × 104 ppm
2.34 × 1023 atoms
150 mL
10.
(a)
(b)
(c)
4.94 × 10!2 mol
0.172 g
60.8%
11.
(a)
(b)
(c)
(d)
(e)
(f)
(g)
Zn2+(aq) + 2 OH!(aq) ÿ Zn(OH)2(s)
1.50 g NaOH
NaOH is the limiting reagent
1.86 g Zn(OH)2
0.0750 mol L!1
2.00 g ZnCl2 leftover; all NaOH used up
84.8%
12.
Hg(R) + 2 S(s) + 2 C(s) + N2(g)
13.
Br2(R);
14.
!20 kJ
K(s);
H+(aq)
ÿ
MgCO3(s) + H2O(R)
4.4 × 10!8 mol L!1
ÿ
(units:
mol
)
L
Avogadro’s number = 6.022 × 1023 atoms mol!1
1 ppm = 1 mg L!1
1 ppb = 1 µg L!1 = 1 × 10!3 ppm
1.
n(x)
V(x)
Hg(SCN)2(s)