O level chemistry 2019 5070/42 Answers

5070/42 Answers
Q1)Table: 23.6, 0.3 Tick on 23.6 and 23.8
Mean 23.7
Moles of HCl: 0.01398
Moles of Magnesium Hydroxide: 0.00699
Mass of Mg(OH)2: 0.405(42)
Mass of Milk Of Magnesia : 11.7
% = 3.46~
Q2) Chromatography se karna tha

Electro Chemistry:
Cathode: pink deposits
Anode : Colorless gas.
Observation with inert: blue color fades away
COLOR CHANGE WITH Cu electrodes: No change.
Mass of Anode Decrease
Mass of Cathode increase

Graph Question:
Color Change of Sol; Colorless to Brown
Q) Why did addition of CaCO3 stopped rxn.
A) Acid was nuetralized...
Anomalous Point : 100,11.0
Volume: 13.0~15.0 (Depends on Graph)
Time : 85~95 (Again Depends on Graph)
The gradient at 50s was steeper than At 400s
Reason : More molecules, more effective collision, high Rate of Reaction.

PREPARATION OF SALTS:
a)
1. Excess CuCO3 in Sulfuric acid.
2.Heat/Stir
3.Filter
4. CRYSTALLISATION
5. WASH AND DRY.
b)
1. Silver Nitrate + Ammonium Chloride
2. Mix, Stir.
3. Filter
4. Wash and dry.

Identification of Cation Anion Table:
Carbonate Ion present. + CO2 gas.
White ppt of BaSO4
White PPt, Insoluble
No Observations.

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