Chemistry mocks deb papers

Jayeire

DEB papers for Chemistry ny1?:eek:

euwwy deuwwy

I had someone else send this to me before my chemistry mock, its only fair to share the wealth, as long as im not too late, its DEB btw

Section A
Answer at least two questions from this section [see page 1 for full instructions].
1. A mass of 8.82 g of ammonium iron(II) sulfate crystals ((NHOiSC^.FESC^.JcI^O) was dissolved in
deionised water to which some sulphuric acid had been added. The solution was then made up accurately to 250 cm3. A pipette was used to transfer 25 cm3 of this solution to a conical flask to which some dilute sulfuric acid had been added. A burette was filled with a 0.02 M solution of potassium manganate(VII) and a number of titrations were carried out. The mean titration result was 22.5 cm3.
The titration reaction is described by the equation:
MnO7 + 5Fe2+ + 8H+ - *• Mn2+ + 5Fe2+ + 4H2O
(a) Why was sulfuric acid added in making up the ammonium iron(II) sulfate solution? (5)
(b) Describe the correct procedure for diluting the ammonium iron(II) sulfate solution and making up the
250 cm3 solution from the crystals. (12)
(c) What colour change is observed as the solution from the burette is titrated into the conical flask? How is
the end-point of the titration detected? (9)
(d) During the titration, drops of the potassium manganate(VII) solution were noticed high on the sides of
the conical flask. What action could be taken to deal with this problem? Why is it possible to take this
action without affecting the overall result of the titration? (6)
(e) What is the purpose of the sulfuric acid in the conical flask? What would be observed if insufficient
acid was present during the titration? (6)
(/) Calculate the concentration of the ammonium iron(II) sulphate in the solution in
(i) grams per litre,
(ii) moles per litre.
Hence, find the percentage water of crystallisation present in the ammonium iron(II) sulfate crystals and
the value of x, the degree of hydration of the crystals. (12)



2. To prepare a sample of soap, about 5 g of lard (source of a long-chained ester), 4 g of potassium hydroxide (excess) and 50 cm3 ethanol were placed in a large boiling flask fitted with a condenser. The mixture was refluxed for about 30 minutes. The apparatus was then rearranged for distillation. After the distillate was removed the remaining mixture was quickly transferred into a beaker containing 100 cm3 of brine. The solution was then filtered to remove the soap.
(a) What term is used to describe the reaction that takes place between the long-chained ester and the
potassium hydroxide? (3)
(b) What is the function of the ethanol in the reaction? (3)
(c) What other substance is added to the reaction flask prior to refluxing? (3)
(d) Draw a labelled diagram of the apparatus used to reflux the mixture for 30 minutes. Explain why this
type of apparatus was used. (14)
(e) One of the products of the reaction is an alcohol. Name this product and give its structural formula.
(9)
(/) What is brine? What is the purpose of pouring the mixture into the brine? (9)
(g) Explain what happens when a sample of this soap is added to hard water. (9)
3. In an experiment to determine the heat of reaction of 0.5 M hydrochloric acid and 0.5 M sodium hydroxide, 200 cm3 of the acid and the same volume of base were measured into two separate containers. The initial temperature of both was taken and found to be 14.5 °C. The acid was added to the base and the solution was stirred. The highest temperature recorded was found to be 17.9 °C.
(a) Define the term heat of reaction. (8)
(b) What material could be used for the containers that the acid and base are measured into? Explain your
answer. (9)
(c) What precautions should be taken to ensure an accurate measure of the rise in temperature? (6)
(d) The density and specific heat capacity of the resulting solution (assumed equal to that of water) are
1.0 g cm"3 and 4,200 J kg'1 °C~' respectively. Calculate the heat of reaction. (12)
(e) Draw an energy profile diagram for an exothermic reaction. Mark clearly on the diagram
(i) the activation energy,
(ii) the heat change for the reaction. (9)
(/} If the base used had been ammonia, the heat of reaction would have been less. Explain why this would
be the case. (6)



Section B
[See page 1 for instructions regarding the number of questions to be answered]
4. Answer eight of the following parts (a), (b), (c), etc. (50)
(a) Identify the atom or ion with the electronic configuration (/) [Is22s22p6]2+, (if) Is22s22p63s23p64s13d5.
(b) What is the octane number of a motor fuel?
(c) How many carbon atoms are present in 800 cm3 of propane, C3H8, at s.t.p.?
(d) Explain the meaning of the term heat of combustion.
(e) Write a balanced equation to describe the reaction at the cathode when an electric current is passed
through sodium sulphate solution.
(/) State Gay-Lussac 's law of combining volumes.
(g) What is radioactivity?
(h) Explain why phosphorus has a greater first ionisation energy than sulfur.
(/) State two uses of aromatic compounds.
(/) What flame colour would be observed when (/') a lithium salt (e.g. LiCl) and (if) a sodium salt (e.g. NaCl) are heated in a Bunsen flame?
(k) Answer part A or part B.
A Name two greenhouse gases.
or B Name the main ore of (/') aluminium and (if) iron.
5. (a) (i) Discuss the contributions of Dobereiner and Mendeleev to the development of the periodic
table. (12)
(ii) State two differences between Mendeleev form of the periodic table and the modern table. (6)
(b) (i) Define electronegativity. (5)
(if) Describe and account for the trends in electronegativity of the elements across the second period
of the periodic table. (7)
*
(Hi) Use electronegativity values to predict the bonding in (a) phosphine, PH3, and (b) potassium
chloride, KC1. (6)
(zv) Show by means of suitable diagrams, the formation of the bonds in (a) phosphine, PH3, and
(b) potassium chloride, KC1. (8)
(v) Explain why potassium chloride has a considerably higher boiling point than phosphine. (6)



6. Examine the reaction scheme and answer the questions which follow.
A X B Y C
CH3CH=CH2 * CH3CHC1CH3 * CH3CHOHCH3
Z I H+/Na2Cr2O7 D
(a) Give the systematic IUPAC name of compound A. (3)
(b) Which of the reactions X, Y or Z is an addition reaction? Name the reagent used in this reaction.
Briefly describe the mechanism of this reaction. (17)
(c) Compound C is a secondary alcohol. Explain what this means and give the name and structural formula
of its corresponding primary alcohol. (12)
(d) Identify compound D. Describe how you would convert it back to compound C. (9)
(e) What, if anything, would be observed when
(/') silver nitrate (Tollens reagent) is added to D,
(if) bromine solution is added to A,
(til) sodium is added to C? (9)
7. (a) What is a catalyst! (5)
(b) Catalytic converters are fitted in all modern cars with petrol engines.
(/) Identify two elements used as catalysts in catalytic converters. (6)
(if) Why is leaded petrol not suitable for use in cars fitted with catalytic converters? (3)
(Hi) Identify one reaction that is catalysed by the catalytic converter in a car. Give one environmental
benefit of this process. (9)
(c) (/') Define rate of reaction. (5)
(if) Describe, using simple experiments, how you would demonstrate the effect of (a) particle size
and (b) concentration on the rate of a chemical reaction. (18)
(Hi) Name two other factors which affect the rate of a chemical reaction. (4)
8. (a) (/) Explain the meaning of the term pH. Name one method by which the pH of a solution can be
measured. (7)
(if) What is a conjugate acid base pair? (3)
(///) Identify the conjugate acid base pairs in the following equation. (6)
H2S04 + H2F2 * H3SOt + HF~
A certain indicator is a weak acid. It dissociates in water at 25 °C. It is represented by the equation.
HIn > H+ + In"
(/v) Calculate the pH of a 0.01 M solution of the indicator at 25 °C given that Ka = 2 x 10~5. (9)
(b) (i) What is meant by hardness in water? (3)
(//) Distinguish between temporary and permanent hardness in water. (6)
(Hi) What compound causes temporary hardness? Explain how this compound gets into water. (9)
(iv) A white deposit is often found on the inside of kettles in hard water districts. Write an equation
for the reaction involved in producing this deposit. (7)



(a) State Ze Chdtelier 's principle. (6)
In an experiment 3 g of hydrogen and 381 g of iodine were mixed and allowed to come to equilibrium in a sealed vessel at 623 K. The equilibrium reaction is represented by the equation:
AH = -12.5 kJ mo!"1
(b) Write an equilibrium constant expression (Kc) for the reaction. (5)
(c) Why is it not necessary to know the volume of the sealed vessel to calculate Kc for this reaction? (6)
(d) If the equilibrium constant Kc is 64 at 623 K, calculate
(/) number of moles,
(ii) mass of hydrogen iodide present,
in the equilibrium mixture at this temperature. (1 5)
(e) How would the yield of hydrogen iodide be affected if the reaction was carried out:
(i) at a lower pressure,
(//) at a higher temperature?
Give a reason for your answer in each case. (12)
(f) If the equation had been written in the form:
2HIfe) ;==^ H2(g) + I2fe) AH = +12.5 kJ mol1
What effect, if any, would this have on the value of Kc? (6)
10. Answer any two of the parts (a), (b) and (c). (2 x 25)
(a) Define the mole. (6)
A mass of 3.24 g of calcium hydrogen carbonate (Ca(HCO3)2) was added to 200 cm3 of 0.1 M solution of hydrochloric acid.
The reaction proceeded according to the equation.
Ca(HCO3)2 + 2HC1 + CaCl2 + 2CO2 + 2H2O
(/) Identify which of the two reactants is the limiting factor. (9)
(ii) Calculate the mass of calcium chloride produced by the reaction. (4)
(Hi) Calculate the maximum volume of carbon dioxide that would be produced at s.t.p. (6)
(b) The general Gas Equation for an ideal gas is PV= nRT.
(i) What is an ideal gas? (5)
(ii) Give two reasons why real gases depart from ideal gas behaviour. (6)
(Hi) Under what conditions of temperature and pressure do real gases come closest to ideal behaviour?
(6)
In an experiment to determine the relative molecular mass of a volatile liquid, it was found that 0.3 g of the gas occupied 1.68 x 10"4 m3 at 300 K at a pressure of 1 x l O5 Nirf2.
(iv) Calculate the relative molecular mass of the gas. (8)
(c) (i) From the period (Na to Ar) on the periodic table, identify (a) a solid metallic element which is
divalent in its compounds, (b) a solid metallic element which is trivalent in its compounds and
(c) a gaseous element which is often monovalent in its compounds. In what molecular form does
the gaseous element exist? (12)
(ii) Oxygen combines with each of these elements. Write down the formula of a compound of each of
these elements with oxygen. (9)
(Hi) The oxides of the trivalent compound is classified as being amphoteric. What does this mean? (4)




11. Answer any two of the parts (a), (b) and (c). (2 x 25)
(a) (/) Explain the meaning of the term isotopes. (5)
(ii) Describe briefly the processes that occur in a mass spectrometer. (15)
Copper exists in two isotopes, 29Cu and 29 Cu. Using a mass spectrometer, it was found that copper consists of 70% ^Cu and 30% ^Cu.
(Hi) Find the relative atomic mass of copper. (5)
(b) Define oxidation number. (4)
Using oxidation numbers, identify which species is being oxidised and which species is being reduced in
the following reaction: (12)
Cr2O," + S + H+ > Cr2O3 + SO2 + OH"
Hence, or otherwise balance the equation (9)
(c) Answer part A or part B
A
(i) Explain the terms (a) feedstock, (b) co-products, as they relate to industrial chemistry. (6)
(ii) In relation to an industrial case study you have undertaken, describe the processes that are carried
out by means of chemical equations. (12)
(Hi) How does this industry cope with the control of effluent and waste disposal? (7)
or
B
(i) Explain the terms (a) addition polymer, (b) monomer. (6)
(ii) Draw the structural formula of a monomer and two units of a polymer of your choice. Name
one use for this polymer. (12)
(in) What is the difference between high density and low density polyethene? (7)

Jayeire

Thank u sooooooooooooooo much!! total ledge!!!