QUESTIONS
Q1 You are provided with
 Metal carbonate M_{2}CO_{3} solid Q which weighs exactly 5.0g
 2M hydrochloric acid solution P
 Sodium hydroxide solution R made by dissolving 40g of the solid in a litre of solution.
You are required to determine
The relative formula mass (RFM) of M_{2}CO_{3} and hence the relative atomic mass (RAM) of M.
Procedure
 Measure accurately using a measuring cylinder 100cm3 of solution P into a clean 250cm^{3} conical flask.
 Add all the 5.0g of solid Q,shake well and wait for effervescence to stop.
 Put the solution into a 250ml clean beaker.
 Label the resulting solution S.
 Pipette 25cm^{3} of solution R into a clean conical flask and add 23 drops of phenolphthalein indicator
 Fill the burette with solution S and titrate against solution R.
 Record the results in the table below
 Repeat the titration two more times and record in the table. (4mks)
I  II  III  
Final burette reading  
Initial burette reading  
Volume of S used(cm^{3}) 
 Calculate the average volume of solution S used (1mk)
 Calculate:
 Moles of sodium hydroxide solution R used (2mks)
 Moles of hydrochloric acid solution S in the average volume used (2mks)
 Moles of HCl solution S in 100cm the of solution. (2mks)
 Moles of hydrochloric acid solution P in the 100cm^{2} of the original solution (2mks)
 Moles of HCl solution P that reacted with solid Q (2mks)
 Moles of M_{2}CO_{3} solid Q that reacted (2mks)
 The RFM of M_{2}CO_{3} (2mks)
 The RAM of metal M (1mk)
(Na=23 O=16, H=1)
Q2 Carry out the tests on the substances given and record your observations and inferences in the spaces provided.

 Put half of solid A in a boiling tube, add about 3cm^{3} of distilled water shake and retain the solution
Observation Inference  To the solution above, add a few drops of ammonia solution then add in excess
Observation Inference  Scoop the rest of solid A in a clean metallic spatula and burn on a nonluminous flame.
Observation Inference
 Put half of solid A in a boiling tube, add about 3cm^{3} of distilled water shake and retain the solution

 Put ½ of solid B in a test tube and add about 1cm3 of distilled water
Observation Inference  Put the remaining solid in a test tube and add about 1cm3 of dilute hydrochloric acid.
Observation Inference
 Put ½ of solid B in a test tube and add about 1cm3 of distilled water

 Put ½ of solid C in a test tube,heat gently then strongly observing the colour changes in the solid when heating and after cooling. Test any gas produced with wet litmus papers and a glowing splint.
Observation Inference  Put the remaining solid C in a test tube and add about 2cm3 of distilled water,shake well. Add ammonia solution drop wise then in excess
Observation Inference
 Put ½ of solid C in a test tube,heat gently then strongly observing the colour changes in the solid when heating and after cooling. Test any gas produced with wet litmus papers and a glowing splint.
 Put solid D in a test tube and add 2cm^{3} of distilled water. Shake well then add ammonia solution drop wise then in excess.
Observation Inference  Repeat procedure in (d) above with solid E.
Observation Inference  Divide solution F into 3 portions.
 Test the PH of the first portion with universal indicator.
Observation Inference  In the second portion drop a piece of magnesium ribbon and test for any gas produced with a burning splint.
Observation Inference  To the third portion add a ¼ spatula of sodium hydrogen carbonate.
 Test the PH of the first portion with universal indicator.
MARKING SCHEME
Q1
 Table 3 titrations  1mk
2 titrations  1/2mk
1 titration  0mk  Decimals 1dp or 2dp used consistently  1mk
(if 2dp,the 2nd should be a 0 or 5)  Accuracy Compare with any of SV within + 0.1  1mk
+0.2  1/2mk  Principles of averaging
2 0r 3 consistent values averaged  1mk
: penalize 1/2mk for arithmetic error  Final answer ____ 1mk
Within + 0.1 of SV  1mk
+ 0.2 of SV ______ 1/2mk See 4 and 5 above (≈ 23.5cm^{3})
 ^{ }
 ^{40g}/_{40} = 1M
No of moles = 1 x 25 = 0.025 moles of NaOH
1000  NaOH + HCL → NaCl + H_{2}O
Mole ratio
NaOH : HCl
1 : 1
0.025 : ? = 0.025 moles of HCl  0.025 moles = X (volm from (a) above)
? = 100cm^{3}
0.025 x 100 = 2.5moles of HCl
X X  2 moles  1000cm^{3}
? 100cm^{3}
= 100 x 2 = 0.2 moles of P
1000  (0.2 ^{ 2.5}/_{X}) moles of HCl
 M_{2}CO_{3} + 2HCl → 2MCl + CO_{2} + H2O
Mole ratio
M_{2}CO_{3} : HCl
1 : 2
?  0.2 – ^{ 2.5}/_{X}
= (0.2 – ^{ 2.5}/_{X}) x ½ = moles of Q  RFM = 5.0
( 0.2 ^{ 2.5}/x) x ½  2M + 60 = 5.0
(0.2 ^{ 2.5}/x)x ½
M = ½( 5.0  60)
(0.2 ^{ 2.5}/x)x ½
 ^{40g}/_{40} = 1M
Q2
Observation  Inference 


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