St Peter the Apostle High School
Chemistry Department
The Mole &
Reacting Mass Calculations
N4 & N5 Homework Questions
Answer National 5 level
questions as directed by your
teacher.
National 4 Questions
Formula Mass Revision
1.
Work out the formula mass of the following compounds:
(a)
(c)
(e)
(g)
(i)
NaCl
C2H5OH
carbon monoxide
potassium nitrate
copper (I) oxide
(b)
(d)
(f)
(h)
(j)
HBr
MgF2
chlorine gas
barium chloride
aluminium oxide
(10)
National 5 Questions
The Mole
1. Calculate the mass of 1 mole of the following:
(a)
(c)
(e)
(g)
(i)
2.
C3H8
H2SO4
nitrogen gas
sodium carbonate
calcium nitrate
(b) Mg(NO3)2
(d) Li3 PO4
(f) copper (I) hydroxide
(h) potassium sulphate
(j) ammonium chloride
(10)
(b) 0.75 moles C6H12O6
(d) 20 moles NaOH
(f) 6 moles AgCl2
(12)
(b) 10 moles of magnesium
(d) 5 moles of sulphur dioxide
(f) 0.1 moles of calcium chloride
(18)
(b) 100g Mg3N2
(d) 8.2g Ca(NO3)2
(f) 0.5g H2
(12)
Calculate the mass of:
(a) 0.5 moles CaSO4
(c) 4 moles H2
(e) 0.3 moles Fe2O3
3. Calculate the mass of:
(a)
(c)
(e)
2 moles of oxygen
5.5 moles of potassium chloride
3 moles of sodium sulphate
4. Calculate the number of moles in:
(a)
(c)
(e)
9.8g H2SO4
36g C
98g C7H14
5. Calculate the number of moles in:
(a)
(c)
(e)
1.6g methane
5.6g carbon monoxide
9g water
(b) 6.4g copper (II) sulphate
(d) 8.2g calcium nitrate
(f) 12.7g iodine
6.
7. Ethanol, C2H5OH, is the alcohol found in whisky. A bottle of whisky contains 230g of
ethanol. Calculate the number of moles of ethanol present in the whisky.
(2)
8. A strip of rhubarb was found to contain 1.8g of oxalic acid. How many moles of oxalic
acid, C2H2O4, are contained in 1.8g?
(2)
Reacting Mass Calculations (See also Fuels Unit 2 Homework)
1. (a)
(b)
Calculate the mass of water produced when 0.2g of hydrogen is burned in air.
Calculate the mass of hydrogen needed to produce 0.72g water in the same
reaction.
(3)
(3)
2. Calculate the mass of calcium oxide formed when 10g of calcium carbonate decomposes
as per the equation :
CaCO3 (s)
CaO (s)
+
CO2 (g)
(3)
3. The equation for calcium burning in oxygen is
2Ca (s)
+
O2 (g)
2CaO (s)
Calculate the mass of calcium required to produce 1.12g of calcium oxide.
(3)
4. Calculate the mass of hydrogen produced when 4.9g of magnesium reacts with
an excess of dilute sulfuric acid.
Mg
+
H2SO4
MgSO4
+
H2
(3)
5. Magnesium reacts with dilute hydrochloric acid. The equation is shown:
(a)
(b)
(i) Copy and complete the equation by adding the state symbol for magnesium
chloride.
(ii) State the test for hydrogen gas.
In an experiment 4.9g of magnesium reacted with excess dilute hydrochloric
acid. Calculate the mass of hydrogen produced in this reaction.
(1)
(1)
(3)
6. Silver jewellery slowly tarnishes in air. This is due to the formation of silver (I) sulphide.
The silver (I) sulphide can be converted back to silver using the following appartatus.
The equation for the reaction which takes place in the beaker is shown;
(a)
(b)
Calculate the mass of silver produced when 0.135g of aluminuim is used up.
How would you show that aluminium has been used up?
(3)
(1)
7. Urea reacts with water, breaking down to form carbon dioxide and ammonia.
H2NCONH2
+
H2O
CO2
+
2NH3
Calculate the mass of ammonia produced, in grams, when 90g of urea breaks
down.
(3)
8. The equation for the formation of nitrogen trifluoride , NF3, is:
N2
+
3F2
2NF3
Calculate the mass of nitrogen trifluoride produced from 7g of nitrogen.
(3)
9. Iron is produced in the blast furnace.
(a)
(b)
The key reaction which takes place in zone 3 is shown. Copy this equation
and balance it.
The key equation for zone 2 is also shown. Calculate the mass of carbon
monoxide produced when 1200kg of carbon reacts.
(1)
(3)
10. Gold is a very soft metal. In order to make it harder, goldsmiths mix it with silver.
The quality of the gold is indicated in carats.
(a)
The graph shows information about the quality of gold.
(i) What is the percentage of silver in 18 carat gold?
(ii) Calculate the number of moles of silver in an 18 carat gold ring weighing 6g.
(b)
(1)
(3)
Silver tarnishes in air forming black silver sulphide, Ag2S.
The equation for the reaction is:
What mass of silver sulphide would be formed from 1.08g silver?
(3)