Chemistry 2005 Jamb Examination

C. Invertase

Invertase (sucrase) hydrolyses sucrose into the two monosaccharides glucose and fructose:

\[\mathrm{sucrose + H_2O \xrightarrow{enz} glucose + fructose}\]

A. Alkenes

Permanganate (tetraoxomanganate(VII), MnO₄^-) oxidizes C=C bonds and is decolourized by unsaturated compounds — it is a classical test for alkenes.

B. Propanal and propanone

Both propanal (an aldehyde) and propanone (a ketone) have the same molecular formula C₃H₆O but different connectivity — they are structural isomers.

C. Acidic impurities

Concentrated sodium carbonate (Na₂CO₃) neutralizes and removes acidic impurities such as excess ethanoic (acetic) acid from the ester layer during washing.

A. Two

General formulas: acyclic alkane: C_nH_2n+2; single-ring cycloalkane: C_nH_2n. Therefore the difference is 2 H atoms:

\[\text{Acyclic: }C_nH_{2n+2},\qquad \text{Cyclo: }C_nH_{2n}\] \[\Delta H = (2n+2)-2n = 2\]

D. CH₂=CHI

One equivalent of HI adds to the triple bond of ethyne giving a vinyl halide (iodoethene): CH≡CH + HI → CH₂=CHI (1-iodoethene).

A. Ethene

Ethene (ethylene) is widely used commercially to trigger and accelerate fruit ripening.

The solid substances left behind as scale when water boilers are used in boiling water for a long period of time will contain Magnesium trioxosilicate(IV) and rust which is an indication that the water is hard water(temporary hardness of water, which upon boiling, Calcium and magnesium trioxocarbonate(IV) are formed on the ring ). The rust can occur because of the presence of oxygen and water.

A. 2,500 cm³

Air contains about 1% noble gases by volume (argon ≈0.93% plus trace neon, helium, krypton, xenon). Assuming 1%:

\[ V_{\text{air}}=\dfrac{25\ \text{cm}^3}{0.01}=2500\ \text{cm}^3 \]

B. Temperature

A solubility curve plots solute solubility (usually g solute per 100 g solvent) versus temperature — showing how solubility changes as temperature changes.