In a firework, solid potassium nitrate, KNO3, decomposes to form solid potassium nitrite, KNO2, and oxygen, O2.
(i)
Write a balanced symbol equation for this reaction.
(ii)
Use section 6 of the data booklet to calculate the amount, in g, of potassium nitrate, KNO3, required to make 1.5 g of oxygen. Give your answer to 2 significant figures.
Question 1b
Marks: 1
b)
Use section 2 of the data booklet to calculate the volume of gas at STP, in dm3, that is produced in the reaction outlined in part (a). Give your answer to 2 significant figures.
Question 1c
Marks: 3
c)
Potassium can form a superoxide, KO2 (s), which will react with carbon dioxide, CO2 (g), to produce potassium carbonate, K2CO3 (s) and oxygen, O2 (g), as shown in the equation below.
4KO2 (s) + 2CO2 (g) → 2K2CO3 (s) + 3O2 (g)
(i)
Calculate the amount, in moles, of 5.00 g of potassium superoxide. Give your answer to 3 significant figures
(ii)
Calculate the amount, in moles, and therefore volume, in dm3, of carbon dioxide which will react with the superoxide. Give your answer to 3 significant figures.
Question 1d
Marks: 1
d)
A student calculated that 4.86 g of potassium carbonate, KCO3, should be produced during the reaction outlined in part (c), 2.61 g of potassium carbonate, KCO3, was produced when the experiment was carried out. Calculate the percentage yield for the production of potassium carbonate. Give your answer to 2 decimal places.
Question 2a
Marks: 2
A student carried out a series of titration experiments. Their results from their experiments are shown in the table below.
Titration
Rough
1
2
3
Final reading / cm3
25.45
21.95
43.65
22.10
Initial reading / cm3
0.00
0.05
21.90
0.10
Titre / cm3
25.45
21.90
21.75
22.00
a)
Calculate the mean titre using the concordant results. Give your answer to 2 decimal places.
The student added 0.10 mol dm-3 hydrochloric acid, HCl (aq), to the burette and performed the titration using a 25.00 cm3 sample of an unknown carbonate solution. The equation for the neutralisation reaction is shown below.
The student used 1.38 g of the unknown carbonate to make up a 250 cm3 standard solution for the titration outlined in part (a). Using section 6 of the data booklet, prove that the unknown carbonate is potassium carbonate, K2CO3.
Calculate the amount, in moles, of K2CO3 ………………………………………
Calculate the concentration in, mol dm-3, of K2CO3 solution …………………………………
3.75 g of zinc oxide, ZnO (s), was added to 150 cm3 of 1.00 mol dm-3 of sulfuric acid (aq) producing a salt. Write a balanced symbol equation for this reaction.
Question 3b
Marks: 3
b)
Using the equation in part (a) and section 6 of the data booklet, calculate the limiting reagent in the reaction. Give your answer to 2 significant figures.
Question 3c
Marks: 1
c)
Use your answer to part (b) and section 6 of the data booklet to calculate the amount, in grams, of the salt produced. Give your answer to 3 significant figures.
Question 3d
Marks: 1
d)
Calculate the amount, in moles, of the excess reactant left over at the end of the reaction. Give your answer to 2 decimal places.
Question 4a
Marks: 2
A sample of pure magnesium nitrate, Mg(NO3)2, was decomposed by heating as shown in the equation below
2Mg(NO3)2 (s) → 2MgO (s) + 4NO2 (g) + O2 (g)
A 0.75 g sample of Mg(NO3)2 was completely decomposed by heating.
a)
Calculate the amount, in moles, of magnesium nitrate that was decomposed. Give your answer to 2 decimal places.
90 cm3 ammonia gas, NH3 (g), is combusted in oxygen, O2 (g), to produce nitrogen oxide and water, H2O (l). What is the total volume of gases remaining when 90 cm3 of ammonia is combusted completely with 50 cm3 of oxygen according to the equation shown?
4NH3 (g) + 5O2 (g) → 4NO (g) + 6H2O (l)
Deduce the limiting reagent for the combustion of ammonia, 90 cm3 ammonia gas, NH3 (g), is combusted in oxygen.
Calculate the total volume, in cm3, of gases remaining for the reaction in part (a).
Question 5c
Marks: 1
c)
Sketch a line on the graph below that shows the correct relationship between pressure and
Question 5d
Marks: 2
d)
At 25 oC and 100 kPa a gas occupies a volume of 35 dm3. Using the equation , calculate the new temperature, in oC, of the gas if the volume is decreased to 15 dm3 at constant pressure.