2020 - JAMB Chemistry Past Questions and Answers - page 2

The reaction of calcium carbide with water, producing acetylene and calcium hydroxide, was discovered by Friedrich Wöhler in 1862. This reaction was the basis of the industrial manufacture of acetylene and is the major industrial use of calcium carbide.

In chemistry, a mixture is a material made up of two or more different substances which are not chemically combined. A mixture is the physical combination of two or more substances in which the identities are retained and are mixed in the form of solutions, suspensions and colloids. Wikipedia

Examples include Air, Soil, Palm oil, Seawater, Blood, Crude oil, etc

By applying the combined gas law formula,

Given:

P\(_1\) = 0.825,   V\(_1\) = 2.76 L, V\(_2\) = 1.38 L, P\(_2\) = ?

T1 = T2; we would have P\(_2\) = [ P\(_1\) X V\(_1\) ] ÷ V\(_2\)

[0.825 X 2.76]  ÷ 1.38

= 1.650atm

They are the most stable because they have the maximum number of valence electrons their outer shell can hold.

Hence, they rarely react with other elements since they are already stable.

NH\(_4\)NO\(_3\) Ammonium Trioxonitrate(V) decomposes on heating to give nitrogen(i)oxide N\(_2\)O and water, unlike all other metallic trioxonitrates(v).

The element is Phosphorus in group 5 with valencies of 3 and 5. These are contained in the third energy level of the atom. Due to the number of valence electrons, Phosphorus is capable of forming three bonds with other elements.

500cm\(^3\) of the gas weighed 1.58

22400cm\(^3\) of the gas weight:

[22400 X 1.58g] ÷ [ 500 ]

= 74

Nitrogen(I)Oxide rekindles a brightly glowing splinter but extinguishes a feebly glowing one which is not hot enough to decompose the gas to liberate oxygen

The ammonia molecule has a trigonal pyramidal shape with three hydrogen atoms and an unshared pair of electrons attached to the nitrogen atom. It is a polar molecule and is highly associated because of strong intermolecular hydrogen bonding.

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