C1 Py(pendang)

PSPM1

: MATTER

Session 1999/2000 - January Intake Section A 1.

Oxalic acid is commonly used to remove blood and rust stains. It consists of 2.24% hydrogen, 26.65% carbon and 71.08% oxygen by mass. The molar mass of oxalic acid is 90.0 g mol-1. (a)

Determine the empirical formula of oxalic acid.

(b)

What is its molecular formula?

(c)

500 mL of oxalic acid solution is prepared by dissolving 10.0 g oxalic acid in water. The solution has a density of 1.05 g mL-1. Calculate the molarity and molality of the solution. (CHO2, C2H2O4, 0.222 M, 0.216m)

Section B 2.

Two common isotopes of chlorine are 35Cl and natural occurring isotopes are as follows: 35 37

Cl Cl

=

37

Cl. The relative abundances of the

3. 127 1

(a)

Explain the meaning of isotope by using chlorine as an example.

(b)

With reference to the 12C scale, the relative atomic mass of 35Cl = 34.9689 and 37Cl = 36.9659. Calculate the relative atomic mass of chlorine. (35.45)

3.

When the iron ore haematite, Fe2O3, is heated in a furnace with carbon monoxide, CO, the products obtained are iron and carbon dioxide, CO2. (a)

Write a balanced equation for the reaction.

(b)

If 8.00×104 kg hematite is used, calculate the mass of iron produced.

(c)

Calculate the mass of carbon monoxide needed for the reaction.

(d)

Determine the oxidation state of Fe in Fe2O3 and that of C in CO. (5.60×107 g, 4.20×107 g, +3, +2)

Session 1999/2000 - Jun Intake

KMKCP 2009/2010

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PSPM1

: MATTER

Section A 1.

(a) 1.50 g of metal oxide, MO2, reacts with excess hydrochloric acid solution, HCl, to produce 386 cm3 chlorine gas at STP as given by the following equation: MO2 + HCl → MCl2 + Cl2 + H2O

(b)

i.

Balance the above equation.

ii.

Determine the relative formula mass of MO2 and relative atomic mass of M.

In a separate experiment, 0.20 g of MO2 was added to 25 mL of 0.10 M hydrochloric acid solution. i.

Determine the limiting reactant.

ii.

Calculate the mass of MCl2 produced in the reaction. (87.0, 55.0, 0.079 g)

Section B 2.

The air contains 21% oxygen gas. Natural oxygen gas consists of three isotopes: 16 O, 17O and 18O. (a)

Write the molecular formulas of oxygen gas that exist in the air that show the combinations of those isotopes.

(b)

What is the molar mass of the heaviest oxygen molecule? (36 g mol-1)

3.

(a)

What is a limiting reactant?

(b)

Aluminium reacts with sulphuric acid solution, H2SO4, to produce aluminium sulphate, Al2(SO4)3 and hydrogen gas. If 10.0 g of aluminium reacts with 60.0 g of sulphuric acid to produce 57.0 g of aluminium sulphate solid, determine the limiting reactant. Calculate the theoretical yield and percentage yield of aluminium sulphate. (63.3 g, 90.0%)

Session 2000/2001 - January Intake Section A

KMKCP 2009/2010

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PSPM1

1.

: MATTER

0.40 g of dry sodium hydroxide, NaOH, is dissolved in water to produce 100 mL solution. 25 mL of the solution is used to neutralize a sample of sulphuric acid solution, H2SO4. (a)

Calculate the molarity of the sodium hydroxide solution.

(b)

Write a balanced equation for the neutralization reaction.

(c)

Calculate the number of moles of H2SO4 in the acid solution. (0.10 M, 1.25×10-3)

Section B 2.

Compound P with a relative molecular mass of 46 contains only carbon, hydrogen and oxygen. A 2.30 g sample of P was completely burned in excess oxygen to produce 4.40 g of carbon dioxide gas, CO2 and 2.70 g of water, H2O. Calculate the mass of carbon, hydrogen and oxygen in 2.30 g of P. Determine the empirical and molecular formula of P. Then, write a balanced equation for the combustion reaction. (C2H6O, C2H6O)

3.

A 50.0 g zinc sample was added to 50.0 L solution containing 3.9 g silver ion, Ag + per litre. The reaction was as follows: Zn + 2Ag+ → Zn2+ + 2Ag Was the added zinc enough to completely react with all the silver ions in the solution? Explain your answer. (not enough; 0.765 mol Zn present, 0.904 mol Zn needed)

Session 2000/2001 - Jun Intake Section A 1.

The neutralization reaction between sulphuric acid, H2SO4, and sodium hydroxide, NaOH, yields sodium sulphate, Na2SO4, and water. (a)

Calculate the number of mole of sodium hydroxide needed to produce 0.0800 mol of sodium sulphate.

(b)

Calculate the mass of sulphuric acid needed for the reaction in 1(b). (0.160 mol, 7.84 g)

2.

(a)

What is meant by percentage yield?

(b)

The combustion reaction of potassium chloride, KCl produces potassium chlorate, KClO3 as shown by the equation: 2KCl(s) + 3O2(g) → 2KClO3(s) Calculate the mass of oxygen used to produce 3.8 g potassium chlorate if the percentage yield is known to be 86.0%. (1.73 g)

KMKCP 2009/2010

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PSPM1

: MATTER

Session 2001/2002 Section A 1.

(a)

Define isotope

(b)

A sample of natural occurring chlorine contains 76% 35Cl and 24% 37Cl. Calculate the relative atomic mass of chlorine if the isotopic mass of 35Cl and 37 Cl are 34.96 amu and 36.97 amu respectively. (35.44)

Session 2002/2003 Section B 2.

10.64 g of metal oxide, M2O3, reacts with excess hydrogen gas to produce 3.78 g of water, H2O and metal M as shown by the equation: M2O3(s) + 3H2(g) → 3H2O + 2M(s) Calculate the relative formula mass of M2O3, relative atomic mass of M and mass of M produced in the reaction. (152, 52, 7.28 g)

Session 2003/2004 Section B 1.

A concentrated sulphuric acid solution, H2SO4, of 95.0% by mass has a density of 1.84 g mL-1. Calculate the molarity of the concentrated acid and its volume needed to prepare 1.0 L of 0.080 M sulphuric acid solution. (17.8 M, 4.5 mL)

Session 2004/2005 Section A 1.

A hydrate of potassium carbonate has the formula K 2CO3.xH2O. From 10.00 g of the hydrate, 7.95 g of anhydrous salt was left after heating. Determine the value of x in the formula. (2)

Section B

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: MATTER

A 3.80 g sample of bronze was dissolved in sulphuric acid. The copper in the alloy reacted with sulphuric acid according to the equation Cu(s) + 2H2SO4(aq) → CuSO4(aq) + SO2(g) + 2H2O(l) The CuSO4 formed in the reaction was mixed with sufficient KI to produce CuI(s), I3and SO42- ions. The I3- ion formed in the second reaction was then titrated against thiosulphate, S2O32- solution to form I- and S4O62- ions. (a)

Write the ionic equations for the last two reactions.

(b)

Calculate the percentage by mass of copper in the bronze sample if 26.20 mL of 1.05 M S2O32- solution was consumed in the titration. (46%)

Session 2005/2006 Section A

2.

A sample of concentrated hydrochloric acid contains 38.0% HCl by mass and has a density of 1.1977 g mL-1. Calculate the solution’s (a)

molarity.

(b)

molality. (12.5 M, 16.8 m)

KMKCP 2009/2010

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