Test: Unit 1 - Quantities in Chemistry
Name:
/60
1 mole = 6.02 x 10 23 particles = 22.4 L at STP = molar mass
C = n/V
n=m/MM
% yield = (actual/theoretical)*100
Knowledge and Understanding (17 marks)
1. For the expression 5 C3H8 (g) (1 mark each):
a) How many moles of the compound are represented? ____________________
b) What volume is represented at S.T.P.? ____________________
c) Indicate the number of moles of carbon present. ____________________
d) What is the molar mass? ____________________
e) How many water molecules can be made? ____________________
2.
a) Calculate the number of molecules in 250 g of CS2. (2 marks)
b) How many moles of Hydrochloic acid are in 500mL of 0.350mol/L solution of HCl. (2 marks)
c) What will the new molar concentration of hydrochloric acid be if 200 mL of water is added to
500 mL of 0.350 mol/L HCl solution. (2 marks)
3.
4.
What is the percent, by mass, of hydrogen in water? (3 marks)
Calculate the volume of chlorine gas which could be produced from 250 g of iron (III) chloride.
(3 marks)
FeCl3 (s) →
Fe (s)
+ Cl2 (g)
Inquiry (14 marks)
4. a) Aspirin (C9H8O4) is prepared by heating salicylic acid (C7H6O3) with acetic anhydride(C4H6O3)
according to the following balanced chemical equation. If 4.00 g of salicylic acid are heated
what mass of aspirin is produced? (This is the theoretical yield.) (4 marks)
C7H6O3
+
C4H6O3
→
C9H8O4
+
C2H4O2
b) In an experiment only 4.36 g of aspirin is produced in the above reaction (this is the
experimental yield). What is the percent yield? (3 marks)
5. Calculate the mass of ZnF2 produced when an excess of zinc is reacted with 40.0 mL of 0.25 mol/L
hydrofluoric acid according to the following unbalanced chemical equation. (6 marks)
Zn
+
HF
→
H2
+
ZnF2
Communication (14 marks)
6.
Define any three of the following terms. (2 marks each = 6 marks)
a) Avogadro’s number
b) molar volume
c) solute
d) limiting reagent
e) stoichiometry
7.
Assume that your friend has missed several chemistry classes and that she has asked you to help her
prepare for a stoichiometry test. Unfortunately, because of other commitments, you do not have
time to meet face to face. You agree to email your friend a set of point-form instructions on how
to solve problems involving chemical reactions. Write the text of this email. Assume that your
friend has a good understanding of the mole (hub) concept. Use the back of the page or a separate
sheet for additional space. (8 marks)
Making Connections (15 marks)
8. Methanol is an alternative fuel for cars. Methanol is made synthetically from carbon monoxide and
hydrogen according to the following unbalanced chemical equation. Calculate the volume of
gaseous methanol, CH3OH, that would be produced when 2.0 L of carbon monoxide, CO, and 6.0 L
of hydrogen are mixed. The equation below may not be balanced. (6 marks)
CO +
9.
H2 →
CH3OH
a) Define the Law of Constant Composition – ratios in chemical formulas and reactions. (2 marks)
b) Below is a word equation followed by some data. Fill in the blanks by entering the mass which
correctly completes each. Be careful, this question is tricky! Your answer to a) should help
you! (7 marks)
hydrogen
+
oxygen
→ water
2.0 g
+
16.0 g
→ 18.0 g
4.0 g
+
16.0 g
→
(i)_____ g
2.0 g
+
8.0 g
→
(ii)_____ g
(iii)_____ g
+ (iv)_____ g
→
27.0 g
1.0 kg
+ (v)_____ kg
→
(vi)_____ g
c) What type of chemical reaction is the above?
BONUS
If the density of a gas is 1.96 g/L at STP., what is the molar mass of the gas?