Protected: NECO CHEMISTRY PRACTICAL ANS HERE NOW(NECO)

1.] Volume of burette | Rough | Ist titre | 2nd titre Final Reading(cm) | 26.00 | 22.40 | 32.24 Initial Reading(cm)| 0.00 | 0.00 | 0.00 Volume of A.(cm) |26.00 | 22.40 | 22.40 Average volume used= ( 22.40 + 22.40 )/2 =22.40cm3 (I) Conc, of A in mol/dm3= mass/molar mass Mass of A is 3.89g/dm3 Molar mass of A(Hcl) = ( 1 + 35.5 ) =36.5 Therefore 38.9/36.5 =0.1066mol/dm3 (ii) Conc. Of B in mol/dm3= CaVa/CbVb = Na/Nb = 0.1066 x 22.40/Cb x 25.00 = 1/1 Cb = 1 x 0.1066 x 22.40/25.00 x 1 Cb = 0.0955mol/dm3 Conc. Of B in g/dm3= molar conc of B x molar mass of B = 0.0955 x 40 = 3.82g/dm3 ====================================================================== (Iii) Conc. Of B in g/dm3= molar conc of B x molar mass of B = 0.0955 x 40 = 3.82g/dm3 1c) It is often used in titrations because of its clear and distinct colour change. Because it changes colour at the pH of a mid-strength acid, it is usually used in titrations for acids. Unlike a universal indicator, methyl orange does not have a full spectrum of colour change, but has a sharper end point. (2i)TEST: Add 5cm3 of distilled water 2 all of X in a beaker. Stir & filter. Keep both d filtrate & residue. OBSERVATION: Salt x dissolve partially in water INFERENCE: salt x is a misture of soluble and insolube salt —————————————————————— (2ii)TEST: Divide d filtrate into two portions. (i) To d first portion add a few drops of dilute HNO3 followed by aqueous solution of AgNO3 OBSERVATION: white precipitate is formed INFERENCE: Cl may present —————————————————————— (2iii)TEST: Add NH3OH in excess to d resulting mixture in B(i). OBSERVATION: The white ppt dissolved in excess NH4OH(aq) INFERENCE: Cl^- is present —————————————————————— (2iv)TEST: To d second[Receiving Text] portion add ammonia solution in drops. OBSERVATION: White ppt is formed which soluble in excess INFERENCE: Zn^2+ is present —————————————————————— (2v)TEST: To d second[Receiving Text] portion add ammonia solution in excess OBSERVATION: White ppt is not soluble INFERENCE: PB^2+ or Al^3+ are likely to present —————————————————————— (2vi)TEST: Dissolve the Residue in above 5cm3 of dilute HNO3, divide the resulting soluble into two portion OBSERVATION: Effervescence occur and a gas that turns lime water milky is evolved INFERENCE: Co2 gas is involved from Co3^2- —————————————————————— (2vii)TEST: To d second portion add aqueous solution of potassium-iodide. OBSERVATION: Yellow ppt is formed INFERENCE: PB2+ is present —————————————————————— (2viii)TEST: Heat & allow to cool OBSERVATION: The ppt desolve and re-appear on cooling INFERENCE: Pb2+ is confirmed 3aii. for the starch iodine test is performed in which the starch reacts with iodine to produce dark blue colour which confirms the presence of starch. for glucose benedict’s and fehling’s test is performed. benedict’s testbr /> 3ai. Inorganic Chemistry/Qualitative Analysis/Tests for anions 3c. Burette Conical flask Pipette 3b. Calcium chloride, a deliquescent salt ====================================================================== (3a) H2S gas turns lead(ii)Ethanoate paper black, but So2 cannot turns lead(ii)Ethanoate paper black (3aii) Iodine solution changes the color of starch to blue-black, but doesn’t change the color to glucose (3aiii) Fused Cacl2 , silicalgel , activated charcoal , pipette , burette , funnel , Retort stand , conical flask. ===COMPLETED=====