SA 1

Question 1

How many oxygen atoms are present in 0.050mol of Al2O3?

Answer 1

1. multiply 0.050 with 3 (3 O atoms)
2. multiply with the avogadro
   9.0 x 10^22

Question 2

What is the correct systematic name for Ca(NO2)2?

Answer 2

Calcium nitrite

Question 3

What is the molar mass of (NH4)3PO4? (with units)

Answer 3

149.0 g mol^-1

Question 4

Balance the equation:
x Fe2(SO4)3 + y KOH → z K2SO4 + w Fe(OH)3

Answer 4

x = 1, y = 6, z = 3, w = 2

Question 5

2NaOH + H2SO4 → Na2SO4 + 2H2O
75.00 mL of 0.625 M sodium hydroxide is required to titrate a 100.0 mL solution of sulfuric acid. What is the concentration of the
sulfuric acid?

Answer 5

1. find the mol of NaOH by n = cV (rmb litres)
2. NaOH is twice of H2SO4, find mol of H2SO4 by multiplying it by 1/2
3. find conc of H2SO4 by c = n/V (litres)
   0.234 M

Question 6

2Ni2O3(s) → 4Ni(s) + 3O (g)
If 5.00 mol of Ni2O3 is decomposed to form 1.40 x 10^2 g of Ni, what is the percentage yield of Ni?

Answer 6

1. you know the theory (140), find actual
2. 5 mol of 2Ni2O3 = 10 mol of 4Ni
3. find m with 10mol x Mr
4. actual/theory x 100
   23.9%

Question 7

2CH3OH(g) + 3O2 (g) → 2CO2(g) + 4H2O(g) ΔH = –1452 kJ mol
How much energy is released when 0.500 mol of oxygen is burnt in excess methanol?

Answer 7

1. 3O2 becomes 0.5mol - multiplier is question/actual (0.5/3)
2. energy is ΔH x multiplier
   - 242 kJ (exothermic, energy released)

Question 8

C(s) + O2(g) → CO2(g) ΔH = -394.0 kJ mol
2CO(g) + O2(g) → 2CO2(g) ΔH = -283.0 kJ mol
What is the enthalpy change (ΔH) for the following equation?
C(s) + 1/2O (g) → CO(g)

Answer 8

write out equations
1. C + O2 –> CO2
2. CO2 –> CO + 1/2O
-252.5 kJ mol–1

Question 9

What is Na3N?

Answer 9

sodium nitride

Question 10

What is Ca3P2?

Answer 10

calcium phosphide

Question 11

What is Na2CO3

Answer 11

sodium carbonate

Question 12

What is Cl2O7?

Answer 12

dichlorine heptaoxide

Question 13

What is H2SO3?

Answer 13

sulfurous acid

Question 14

What is SO32-?

Answer 14

sulfite

Question 15

3.65 g of an oxide of carbon was found to have 2.08 g of carbon. Calculate the percentage by mass of carbon in the compound.

Answer 15

1. % comp = want/total x 100
2. 2.08 / 3.65 x 100
   57%

Question 16

What is the mass of 1.25 x 1024 atoms of silver?

Answer 16

2.24 x 102 g

Question 17

What is the correct formula for nitrous acid?

Answer 17

HNO2

Question 18

What is the correct name of H2CO3?

Answer 18

carbonic acid

Question 19

What is the correct name of Na2HPO4?

Answer 19

sodium hydrogenphosphate

Question 20

What is the mass of 1.25 x 1024 atoms of silver?

Answer 20

1. divide with avocado
2. get mass
   2.24 x 102 g

Question 21

How many moles of hydrogen atoms are there in 43.0 g of pentanol, C5H11OH?

Answer 21

1. find mol
2. mol x atoms (12 H atoms wanted)
   5.86 mols

Question 22

What is the number of oxygen atoms present in 14 g of hydrated sodium carbonate, Na2CO3.10H2O?

Answer 22

1. convert to atoms
   3.8 x 10^23 atoms

Question 23

What is the number of moles of chloride ions in 3.85 g of FeCl3?

Answer 23

0.0712 mol

Question 24

A compound with the empirical formula HO has a molar mass of 34 g mol−1. What is its molecular formula?

Answer 24

1. molecular formula = molar mass/Mr
   H2O2

Question 25

An organic compound is known to contain only carbon, hydrogen and oxygen. The compound contains, by mass, 39.1% of carbon and 8.7% of hydrogen. The number of carbon atoms in the empirical formula is

Answer 25

1. divide with each Mr 2. divide with smallest 3

Question 26

What is the percentage composition of sulfur in As2S3?

Answer 26

1. Mr of S / Mr total 39.1%

Question 27

Calculate the mass of barium carbonate produced when excess carbon dioxide is reacted with 0.205 mol of barium hydroxide according to the equation: Ba(OH)2 + CO2 → BaCO3 + H2O

Answer 27

40.4g

Question 28

Lead(II) carbonate decomposes to give lead(II) oxide and carbon dioxide as represented by the following equation: PbCO3(s) → PbO(s) + CO2(g) How many grams of lead(II) oxide will be produced by the decomposition of 2.50 g of lead(II) carbonate?

Answer 28

2.09g

Question 28

Lead(II) carbonate decomposes to give lead(II) oxide and carbon dioxide as represented by the following equation: PbCO3(s) → PbO(s) + CO2(g) How many grams of lead(II) oxide will be produced by the decomposition of 2.50 g of lead(II) carbonate?

Answer 28

2.09g

Question 29

What volume (in mL) of 2.5 % (w/v) salt solution would contain 1.8 g of salt?

Answer 29

1. c = w/v x 100 (in ml) 2. answer / 100 72 mL

Question 30

7.00 mL of a solution of phosphoric acid, H3PO4, neutralised 1.00 x 102 mL of 0.531 M NaOH solution according to H3PO4(aq) + 3NaOH(aq) → Na3PO4(aq) + 3H2O(l) The concentration of the acid is

Answer 30

1. use c1v1 = c2v2 2. rmb to divide 3 2.53 M

Question 31

Carbon monoxide can be oxidised to carbon dioxide. 2CO(g) + O2(g) → 2CO2(g) 3 mol of CO and 2 mol of O2 are mixed. When the reaction is complete, how many mols of O2 will be left?

Answer 31

0.5 mol O2 unreacted.

Question 32

Given the following unbalanced equation. How many moles of Ag2S can be produced when 3.0 mol of Ag, 3.0 mol of H2S and 3.0 mol O2 react? Ag + H2S + O2 → Ag2S + H2O

Answer 32

1. 4Ag + 2H2S + O2 → 2Ag2S + 2H2O 1.5 mol

Question 33

Which reactant in the following reaction is in excess when 15 g of Ca(OH)2 is reacted with 15 g of H3PO4 3Ca(OH)2 + 2H3PO4 → Ca3(PO4)2 + 6H2O

Answer 33

H3PO4

Question 34

The reaction of 5.0 g of fluorine with excess chlorine produced 5.6 g of ClF3. What percentage yield of ClF3 was obtained? Cl2 + 3F2 → 2ClF3

Answer 34

1. find Mr of F2 2. multiply n(F2) with 2/3 3. multiply with Mr of ClF3 (theory 4. 5.6 / theory 69 %

Question 35

18.0 g of magnesium is added to 0.200 L of 2.00 M HCl. The following equation represents the reaction that occurs: Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) What is the mass of magnesium that is left behind when all the HCl reacts?

Answer 35

-13.1 g.-

Question 36

Hydrogen and chlorine can be produced from sodium chloride according to the following reaction. If this process is 65.0% efficient then how much chlorine could be produced from 96.5 g of sodium chloride? 2NaCl + 2H2O → 2NaOH + H2 + Cl2

Answer 36

-38.1 g-

Question 37

What is the percent yield of CO2 if a reaction between 10.0 g CO with 10.0 g O2 produces 12.8 g CO2? 2CO + O2 → 2CO2

Answer 37

81.5 %

Question 38

A chemical reaction has a ΔH of −150 kJ mol–1 and the activation energy for the reverse reaction is +350 kJ mol–1. The activation energy, in kJ mol–1, of the forward reaction is

Answer 38

200

Question 39

C(s) + O2(g) → CO2(g) ΔH = –393.5 kJ mol–1 2H2(g) + O2(g) → 2H2O(l) ΔH = –571.6 kJ mol–1 Given the information above, what is the enthalpy change for the reaction represented by the following equation? C(s) + 2H2O(l) →CO2(g) + 2H2(g)

Answer 39

+178.1 kJ mol–1

Question 40

The decomposition of water can be represented by the following thermochemical equation 2H2O(l) → 2H2(g) + O2(g) ∆H = + 571.8 kJ mol−1 From this equation, it can be concluded that the formation of two moles of liquid water from gaseous hydrogen and oxygen is an a. exothermic process releasing 571.8 kJ of heat energy. b. exothermic process releasing 1143.6 kJ of heat energy. c. endothermic process absorbing 571.8 kJ of heat energy. d. endothermic process absorbing 1143.6 kJ of heat energy.

Answer 40

a. exothermic process releasing 571.8 kJ of heat energy.

Question 41

What does a catalyst do in a reaction?

Answer 41

It provides an alternative pathway of lower activation energy for both forward and reverse reactions

Question 41

What does a catalyst do in a reaction?

Answer 41

It provides an alternative pathway of lower activation energy for both forward and reverse reactions

Question 42

The following equation represents the reaction between hydrogen gas and nitrogen gas. At what rate is NH3 forming when N2 reacts at a rate of 0.50 M min–1 N2(g) + 3H2(g) → 2NH3(g)

Answer 42

1. look at moles 1.0 M min^-1

Question 43

The factor that has the greatest effect on the increase in reaction rate when the temperature increases is that a. the activation energy of the reaction increases. b. the proportion of particles with high kinetic energy increases. c. the activation energy of the reaction decreases. d. the number of collisions between particles increases.

Answer 43

b. the proportion of particles with high kinetic energy increases.

Question 43

The factor that has the greatest effect on the increase in reaction rate when the temperature increases is that a. the activation energy of the reaction increases. b. the proportion of particles with high kinetic energy increases. c. the activation energy of the reaction decreases. d. the number of collisions between particles increases.

Answer 43

b. the proportion of particles with high kinetic energy increases.

Question 43

The factor that has the greatest effect on the increase in reaction rate when the temperature increases is that a. the activation energy of the reaction increases. b. the proportion of particles with high kinetic energy increases. c. the activation energy of the reaction decreases. d. the number of collisions between particles increases.

Answer 43

b. the proportion of particles with high kinetic energy increases.

Question 44

The factor that has the greatest effect on the increase in reaction rate when the temperature increases is that a. the activation energy of the reaction increases. b. the proportion of particles with high kinetic energy increases. c. the activation energy of the reaction decreases. d. the number of collisions between particles increases.

Answer 44

b. the proportion of particles with high kinetic energy increases.