IGCSE Chemistry
CIE IGCSE Chemistry Solved Past Paper Oct/Nov 2019 P41

CIE IGCSE Chemistry Solved Past Paper Oct/Nov 2019 P41


1 ai) K+ ii) Cr3+ iii) Ca2+ iv) Br- v) SO4-

b) Place salt on nichrome wire,then heat using a bunsen flame

c) Mg3(PO4)2 (here valencies are crossed to write formula of the compound)

2a) Atoms of the same element with same number of protons but different number of neutrons

bi) 18 (34-16)

ii) By gaining 2 electrons

iii) Calcium (both have a total of 18 electrons)

ci) (l) + (g) —> (g)

ii) Vanadium(V)oxide, and 450? of temperature

iii) S03 +H2SO4——> H2S2O7

      H2S2O7 + H2O——> 2H2SO4 

di) It causes acid rain (by dissolving in rain water)

ii) Aqueous potassium manganate (Vll) turns from purple to colourless

e) a) Write symbols of elements:

     Na    S    O

b) Calculate moles using mass or % composition given in the question: 29.1/23   40.5/32    30.4/16

= 1.265      1.266       1.9

c) Calculate ratio by dividing all moles with least value (1.265 here)

=     (1 :    1:    1.5) *2 (multiply by 2 to obtain whole numbers)

= Na2S2O3

3a) They can all conduct electricity

b) Water, oxygen

ci) Zinc is more reactive than iron

ii) Fe3+, gains electron

d) Add hydrochloric acid, zinc oxide it dissolves, add sodium hydroxide, zinc oxide dissolves

4 ai) Cobalt carbonate

ii) Lead iodide

b) 2AgNO3 + Na2SO3——> Ag2CO3 + 2NaNO3

c) Pb2+ + 2I- —> PbI2

d) It removes carbonate ions

5 ai) Addition

ii) CH2 (simplest form)

bi) They have the same molecular formula but different structural formula

ii) Butane, propane with methyl group on second carbon in chain

iii) 2C4H10 + 9O2 8CO + 10H2O

6a) Moles = concentration*volume(in dim3)

                 = 0.18*(20/1000) = 0.0036 mol

2 mol of HCL give 1 mol of Na2CO3 from ratio set in equation. So 0.0036mol/2 = 0.0018 mol of Na2CO3

Concentration = moles/volume(in dm3)

                       = 0.0018/(25/1000)= 0.072mol/dm3

b) 0.0048/24 = 0.002mol

ci) Converting moles to mass

      Mass = moles*molar mass

               =   8.89*(1+80)= 720.09g/dm3

ii) Ions in aqueous form can move and carry charge

iii) It is reactive, could react with the products

iv) Bromine gas (more reactive than hydroxide ion,attracted towards positive electrode of opposite charge)

v) 2H+  + 2e-  —–> H2

7a) C6H12O6—–> 2CO + 2C2H5OH

It requires yeast, 30 degrees Celsius of temperature and anaerobic conditions, separated by fractional distillation

b) 5(C-H)  + C-C   +   C-O  + O-H  + 3(O=O)

   (5*413)+  (347)  +    358 + 464   + (3*498) = 4728

4(C=O)  + 6(O-H)  

(4*805)  + (6*464) =6004

Energy change = 4728-6004 = -1276 kJ/mol

ci) It speeds up a chemical reaction without being used itself

ii) 2 carbon atoms share 2 electrons among them. 1 carbon atom shares 1 electron each with 3 hydrogen atoms. The 2nd remaining carbon atom shares one electron with hydrogen and the remaining two with oxygen and so forming a double bond.

iii) Weaker attractive forces in ethanol

di) Moves right because R.H.S has fewest number of molecules

ii) Rate of reaction increases as number of collisions per unit volume increase.

iii) Moves left, because backward reaction is endothermic.

Leave a Reply

Your email address will not be published. Required fields are marked *