Nabteb 2015/2016 Chemistry Practical Available Here

1a.
Volume of pipette used = 25cm3
Tabulate: —- , 1st , 2nd , 3rd
UNDER —- PUT:
Burette Reading (cm3)
Initial burette reading (cm3)
Volume of acide used
UNDER 1ST PUT:
23.50
00.00
23.50

PLS IN NUMBER 1, TAKE NOTE OF UR SCHOOL ENDPOINT OR TITRE VALUE.EACH SCHOOL HAS A DIFFERENT TITRE VALUE FROMUR CHEMISTRY LAB.OUR END POINT HERE IS 21.70cm3.ANYWHR U SEE IT IN OUR WORK, EDIT IT WITH URSCHOOL’S AVERAGE TITRE VALUE.THEN RE-CALCULATE ONCE U EDIT IT IN ANYSOLUTION.

(1)TABULATE:Burrette Readings(cm3),1st Reading | 2ndReading |3rd reading|Final burette Reading|23.70|45.00|26.00|Initial burette Reading|2.00|23.50|4.30|Volume of acid used|21.50|20.70|20.90|Average titre value = (21.70+21.50 + 21.70)cm^3 /3=(64.90)/3= 21.70cm3(1b)A IS 0.100 mol2.50g of Na2CO3 and Na2SO4 in 250cm^3Na2CO3+2HNO3->2NaNO3+H2O+CO2Conc of B in mol/dm^3Conc of Na2CO3 in the mixtureNa2CO3 =106VA=21.7cm^3CA=0.100VB=25cm^3CB=?NA=2NB=1CAVA/CBVB=NA/NB0.1*21.7/CB*25=2/1CB=(0.1*21.7*1)/(25*2)=0.0434M(ii)molar concentration =mass conc/molar massmass conc=molar conc*molar mass=0.0434*106=4.69g/dm^3(iii)2.50g of Na2CO3+Na2SO4->250cm^3Xg of Na2CO3+Na2SO4->1000cm^3Xg=2.50*1000/250Xg=10g% of Na2CO3=4.6/10*100=46%

(2)TABULATE Test | Observation | Inference(i)TEST:Sample C + water 5cm^3 of C + NaoH in drop and inexcess |

OBSERVATION:soluble white gelatinous precipitate in drop. Whitesoluble or dissolve (in excess).

INFERENCE:Soluble salt. Zn^2+ or Al^3+ present.(ii)TEST:5cm^3 of C + NH4OH in drop, then in excess.

OBSERVATION:white geletenous precipitate in drop. Whitegeletenous ppt dissolve in excess.

INFERENCE:Zn^2+ or Al^3+ present. Zn^2+ confirmed (inexcess).(iii)TEST:Solution of sample C + dilute HN3 + BaCl2(aq) + HCl(aq)

OBSERVATION:No visible reaction. White ppt form. White pptinsoluble in dilute Hcl.

INFERENCE:SO3^2- or SO4^2- may be present. SO4^2-confirmed.(iv)TEST:Sample D + dilute Hcl(aq)

OBSERVATION:A colourless and odourless gas evolve with aeffervescence. The gas turn like water milky. The gasturn blue litmus to red

.INFERENCE:The gas in CO2 from CO3^2- or HCO3-(3ai)fountain experiment(3aii)to show that HCL is extremely soluble in water(3aiii)Ammonia gas (NH3)

(3aiv)The water turn red immediately(3av) No(3avi)because of its solubility in water

(3b)u=>(heated) v + CO2CaCo3(s) =>(heated) Cao(s) + Co2(g)v + H20 => wCao(s) + H20(l) => Ca (OH)2(aq)U = CaCa(3), V = Cao, W = Ca (OH)2

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