GREENWOOD HIGH

NAME: ____________________ CLASS: ____________________________

MVK/WS_GR9/MOLES_2023
Instructions:
1. Write down the formula for each problem.
2. Mention all steps clearly
3. Write the answer with unit
WORKSHEET: 2
1. a)Define the following

(i)the mole

...........................................................................................................................................................

........................................................................................................................................................... [1]

(ii)the Avogadro constant

.............................................................................................................................................................

........................................................................................................................................................... [1]

(b)Which two of the following contain the same number of molecules?

Show how you arrived at your answer.
2.0 g of methane, CH4
8.0 g of oxygen, O2
2.0 g of ozone, O3
8.0 g of sulfur dioxide, SO2

1
 ................................................................................................................................................................

................................................................................................................................................................

..................................................................................................................................... ……………..[2]

2. 4.8g of calcium is added to 3.6g of water. The following reaction occurs.

Ca + 2H2O ----------------------------- Ca (OH)2 + H2

a. The number of moles of Ca: ……………………………… (1)

b. The number of moles of H2O:……………………………… (1)

c. Which reagent is in excess? Explain your choice: (2)

……………………………………………………………………………………………………

……………………………………………………………………………………………………

……………………………………………………………………………………………………

……………………………………………………………………………………………………

d. Calculate the mass of the reagent named in (c) which remained at the end of the experiment (1)

……………………………………………………………………………………………………

……………………………………………………………………………………………………

……………………………………………………………………………………………………

3. Chlorine, bromine and iodine are halogens.

(a)Chlorine can be made in the laboratory by heating manganese( IV) oxide with
concentrated hydrochloric acid.

MnO2(s) + 4HCl(aq) → MnCl2(aq) + 2H2O(l) + Cl2(g)

Calculate the volume of 8.00 mol /dm3 HCl(aq) needed to react with 3.48 g of MnO2.

• moles of MnO2 used

................................ mol (1)

2
 • moles of HC l needed

................................ mol (1)

• volume of HC l needed

................................ cm3 (1)

4. Magnesium sulfate crystals are hydrated. Another student heated some hydrated
magnesium sulfate crystals in a crucible and obtained the following results.

mass of hydrated magnesium sulfate crystals = 4.92 g

mass of water removed = 2.52 g

(i)Calculate the number of moles of water removed.

moles of water = ............................. mol [1]

(ii)Calculate the number of moles of anhydrous magnesium sulfate remaining in the crucible.

The Mr of anhydrous magnesium sulfate is 120.

moles of anhydrous magnesium sulfate = ............................. mol [1]

(iii)Calculate the ratio of moles of anhydrous magnesium sulfate : moles of water. Give your
answer as whole numbers.
ratio = ................ : ................ [1]

(iv)Suggest the formula of hydrated magnesium sulfate crystals.

formula of hydrated magnesium sulfate crystals = ............................................ [2]

5. A sample of rust had the following composition:

51.85 g of iron 22.22 g of oxygen 16.67 g of water.

Calculate the following and then write the formula for this sample of rust.

number of moles of iron atoms, Fe = ................... [1]

number of moles of oxygen atoms, O = ................... [1]
number of moles of water molecules, H2O = ................... (1)

simplest mole ratio Fe : O : H2O is .......... : .......... : ..........

formula for this sample of rust is ................... [1]

3
6. When lead( II) nitrate is heated, two gases are given off and solid lead( II) oxide remains.
The equation for the reaction is shown.

2Pb(NO3)2(s) → 2PbO(s) + 4NO2(g) + O2(g)

(a)Calculate the Mr of lead( II) nitrate.

.............................................................................................................................................. [1]

(b)6.62 g of lead( II) nitrate are heated until there is no further change in mass.

(i)Calculate the mass of lead( II) oxide produced.

........................... g [2]

(ii)Calculate the volume of oxygen, O2, produced at room temperature and pressure (r.t.p.).

........................... dm3 [2]

7. Chlorine, bromine and iodine are halogens.

(a)Chlorine can be made in the laboratory by heating manganese( IV) oxide with concentrated
hydrochloric acid.

MnO2(s) + 4HC l(aq) → MnCl2(aq) + 2H2O(l) + Cl2(g)

Calculate the volume of 8.00 mol /dm3 HC l(aq) needed to react with 3.48 g of MnO2.

• moles of MnO2 used

................................ mol

• moles of HCl needed

................................ mol

• volume of HCl needed

................................ cm3 [4]

4
8. The bar charts compare the concentrations of ions in two samples of water, sample A and sample B

(a)Use the information in the bar charts to answer the following questions.

(i)Describe two differences in the composition of sample A and sample B.

................................................................................................................................................................

...............................................................................................................................................................

........................................................................................................................................................... [2]

(ii)Which positive ion has the lowest concentration in sample B?

....................................................................................................................................... ……………[1]

(iii)Calculate the mass of chloride ions present in 100 cm3 of sample B.

Show all your working. [1 dm3 = 1000 cm3]

mass = ...................... mg [2]

9. The following method is used to make crystals of hydrated nickel sulphate. An excess of nickel
carbonate, 12.0g, was added to 40cm3 of sulphuric acid,2.0mol/dm3. The unreacted nickel carbonate
was filtered off and the filtrate evaporated to obtain the crystals.

NiCO3 + H2SO4 NiSO4 + CO2+ H2O

NiSO4+7H2O NiSO4.7H2O

Mass of one mole of NiSO4.7H2O =281g

Mass of one mole of NiCO3= 119g

5
a. Calculate the mass of unreacted nickel carbonate. (3)

Number of moles of H2SO4 in 40 cm3 of 2.0 mol/dm3 acid= 0.08

Number of moles of NiCO3 reacted=

Mass of nickel carbonate reacted =g________

Mass of unreacted nickel carbonate=g______

b. The experiment produced 10.4g of hydrated nickel sulphate. (3)

Calculate the percentage yield.

The maximum number of miles of NiSO4.7H2O that could be formed=

The maximum mass of NiSO4.7H2O that could be formed=

The maximum mass of NiSO4.7H2O that could be formed=g______

The percentage yield=%