IFYCH003 Chemistry
代考化学 All work must be completed independently and without accessing unauthorised materials. The penalty for Examination Misconduct is a mark of zero.
1INSTRUCTIONS TO STUDENTS
| Questions
1-12 |
Answer ALL questions. These questions carry 30 marks in total (60% of the marks for this assessment).
|
| Questions
13-14 |
Answer 1 question ONLY. This question carries 20 marks in total (40% of the marks for this assessment).
|
| The marks for each question are indicated in square brackets [ ]. | |
- Work must be submitted in a single PDF file.
- You must hand write your responses, take a picture and upload it as a single PDF file.
- All work must be completed independently and without accessing unauthorised materials. The penalty for Examination Misconduct is a mark of zero.
- Work must be submitted by the deadline provided. Your Study Centre can be contacted only for guidance on submission of work and cannot comment on the contents of the assessment.
Questions 1-12
Answer ALL questions.
These questions carry 30 marks in total.
Question 1
How many neutrons and electrons does the 34S2- ion have?
| Neutrons | Electrons
|
|
| a)
|
18 | 16 |
| b)
|
18 | 18 |
| c)
|
16 | 18 |
| d)
|
16 | 16 |
Question 2 代考化学
The full electronic configuration of a Cu2+ ion is:
a)1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d7
b)1s2, 2s2, 2p6, 3s2, 3p6, 3d3
c)1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d8
d)1s2, 2s2, 2p6, 3s2, 3p6, 3d9
Question 3
Which of the following molecules or ions has a bond angle of 109.5o?
a)PCl5
b)NH3
c)AlCl4-
d)NH2-
Question 4 代考化学
Which of these contains the most moles of substance?
(1 mol of gas occupies 24dm3 at RTP, room temperature and pressure)
a)1g of hydrogen molecules
b)100cm3 of 2 mol dm-3 hydrochloric acid
c)50g of sodium chloride
d)16dm3 of a gas at room temperature and pressure
Question 5
Which of these reactions is a disproportionation reaction?
a) 3MnO42- + 4 H+ → 2MnO4- + MnO2 + 2H2O
b)(NH4)2Cr2O7 → Cr2O3 + N2 + 4H2O
c)2NaBr + H2SO4 → Na2SO4 + 2HBr
d)Cl2 + 2H2O → 4HCl + O2
Question 6 代考化学
Tungsten can be produced according to the equation:
WO3 + 3H2 → W + 3H2O
Calculate the percentage atom economy of making tungsten by this reaction.
a)77.3 %
b)91.1%
c)100 %
d)20.1 %
Question 7
A student prepares a solution of sodium hydroxide, NaOH, by dissolving 4.36g in distilled water and making up to a total volume of 250cm3. What is the concentration of the solution?
a)0.436 mol dm-3
b)0.109 mol dm-3
c)17.44 mol dm-3
d)0.0273 mol dm-3
Question 8 代考化学
What mass of oxygen is needed to convert 102 g of ammonia into nitrogen?
4 NH3(g) + 3 O2(g) à 2 N2(g) + 6 H2O(g)
a)256g
b)72g
c)144g
d)48g
Question 9
Which of these atoms has the highest electronegativity?
a)Sodium
b)Magnesium
c)Chlorine
d)Fluorine
Question 10 代考化学
What is the name of the strongest force between molecules of hydrogen chloride?
a)Covalent bonds
b)Hydrogen bonds
c)Van der Waals’ forces
d)Permanent dipole-dipole forces
Question 11. 代考化学
An unknown diprotic acid, H2X, reacts with sodium hydroxide as shown in the equation:
H2X + 2NaOH à Na2X +2H2O
1.31 g of the acid was dissolved in deionised water and made up to 250 cm3 solution in a volumetric flask. 25.0 cm3 samples of this solution was titrated against 0.104 mol dm–3 sodium hydroxide solution, requiring a mean volume of 21.45 cm3 for neutralisation.
a)i. The mean volume of sodium hydroxide was calculated from concordant titres. What is meant by concordant titres?
ii. Calculate the moles of sodium hydroxide.
iii. Calculate the moles of the unknown acid in 25cm3.
iv. Calculate the moles of the unknown acid in 250cm3.
v. Calculate the relative formula mass, Mr, of the unknown acid.
b)Predict which of the following pairs of substances has the higher melting point:
i. Na and Mg
ii. NaCl and MgO
c)Explain why the boiling point of chlorine is higher than the boiling point of fluorine.
Question 12.
a)i. Give an equation for the ionisation of a Zn atom to give a Zn+ ion. Include state symbols.
ii. Use the data from a mass spectrum to calculate the relative atomic mass of the sample of zinc. Give your answer to one decimal place.
|
m/z |
64 | 66 | 67 | 68 |
70
|
| Relative intensity | 48.9 | 27.8 | 4.1 | 18.6 | 0.6 |
iii. Explain why zinc is good electrical conductor.
b)Draw a dot and cross diagram:
i.to show the bonding in a molecule of carbon dioxide.
ii.to show the formation of ions in magnesium chloride.
Questions 13-14 代考化学
Answer 1 question ONLY
This question carries 20 marks in total.
Question 13
a)State the oxidation numbers of sulfur in the following:
(i) S8
(ii) H2SO4
(iii) SO32-
b)In the following equation, identify the oxidising agent:
2Al + 3H2SO4 → Al2(SO4)3 + 6H2
c)i. Write a half equation to show the conversion of Fe2+ to Fe3+.
ii. Write a half equation to show the conversion of Cr2O72- to Cr3+.
d)A compound is found to contain, by mass, iron 72.4% and oxygen 27.6%. Calculate the empirical formula. 代考化学
e)Sodium reacts with fluorine to form sodium fluoride. Explain:
i. Sodium fluoride conducts electricity when in solution but not when solid.
ii. Sodium fluoride is brittle.
f)Draw a diagram to show the shape of a molecule of F2O.
Name the shape and give the bond angle.
Explain why a molecule of F2O is this shape.
g)Give the formula of a compound containing fluorine which has an octahedral shape.
h)Draw a diagram to show hydrogen bonding between two molecules of hydrogen fluoride.
Your diagram should include all lone pairs and partial charges.
Question 14
a)3.29g of hydrated calcium chloride (CaCl2.nH2O) was heated to drive off all of water of crystallisation. 1.66g of anhydrous calcium chloride remained.
Calculate the value of n, the number of moles of water of crystallisation.
b)i. The first ionisation energy of fluorine is higher than the first ionisation energy of chlorine. Explain.
ii. The first ionisation energy of fluorine is lower than the first ionisation energy of neon. Explain.
iii. The first ionisation energy of oxygen is lower than the first ionisation energy of nitrogen. Explain. 代考化学
c)Describe a simple test-tube reaction which would distinguish solutions of sodium chloride and sodium bromide. You should name the reagent(s) and observations.
d)State the type of bond formed between a PH3 molecule and a H+ ion. Explain how this type of bond is formed.
e)State the structure and bonding in diamond and explain why it has a very high melting point.
f)Sodium hydrogencarbonate decomposes as shown in the equation:
2NaHCO3(s) → Na2CO3(s) + H2O(g) + CO2(g)
If 2.70 g of sodium hydrogencarbonate is heated calculate the total volume of gas produced at 200oC and 100 kPa. Include a unit with your answer.
(The gas constant is 8.31 J K-1 mol-1).
