2022 - JAMB Chemistry Past Questions and Answers - page 3
Crude petroleum is converted to useful products by the process of?
fractional crystallization
fractional distillation
filtration
chromatography
Fractional distillation is a process used in crude oil refineries to separate (as well as join or split) the various lengths of hydrocarbon chains to create different petroleum products from the different distillates. More.
Users' Answers & CommentsAn organic compound contains 69% carbon, 15.3% hydrogen and 30.7% oxygen. Calculate the the empirical formula [C=12, H = 1, O = 16]
C\(_4\)H\(_12\)O
C\(_3\)H\(_9\)O
C\(_4\)H\(_9\)O
C\(_3\)H\(_8\)O
C \(\frac{69}{12}\) H \(\frac{15.3}{1}\) O \(\frac{30.7}{16}\)
C = 5.75
H = 15.3
O = 1.92
C \(\frac{5.75}{1,92}\) H \(\frac{15.3}{1.92}\) O \(\frac{1.92}{1.92}\)
C\(_3\)H\(_8\)O
Users' Answers & Comments2H\(_2\) + O\(_2\) → 2H\(_2\)O
From the equation above, calculate the volume of unreacted oxygen gas if a mixture of 50cm\(^3\) of hydrogen and 75cm\(^3\) of oxygen is involved
85cm\(^3\)
50cm\(^3\)
125cm\(^3\)
55cm\(^3\)
From the given equation, 2 mol H\(_2\) reacted with 1 mol of O\(_2\)
50cm\(^3\) hydrogen reacted with 25cm\(^3\) oxygen
remainder oxygen = supplied amount - reacted amount
=> 75cm\(^3\) - 25cm\(^3\)
= 50cm\(^3\)
Users' Answers & CommentsIn which of the following will hydrogen form an ionic compound?
HCL
NaH
NH\(_3\)
CH\(_4\)
NaH ionic hydride which is also known as saline (salt-like) hydride, composed of Na+ and H− ions
Users' Answers & CommentsIf the volume of a given mass of a gas at 0ºc is 29.5cm\(^3\). What will be the volume of the gas at 15ºc, given that the pressure remains constant?
31.6
62.2
32.7
31.1
Charles' law states that the volume occupied by a fixed amount of gas is directly proportional to its absolute temperature if the pressure remains constant.
Given that:
V\(_1\) = 29.5cm\(^3\)
V\(_2\) = ?
T\(_1\) = 0ºc or 273k
T\(_2\) = 15ºc or 288k
\(\frac{V_1}{T_1}\) = \(\frac{V_2}{T_2}\)
V\(_2\) = \(\frac{V_1 x T_2}{T_1}\)
=> \(\frac{29.5 x 288}{273}\)
V\(_2\) = 31.1cm\(^3\)
Users' Answers & CommentsThe reactions below represent neutralization reactions, in which of them is the value of ΔH highest?
CH\(_3\)CH\(_2\)COOH + KOH → CH\(_3\)CH\(_2\)COOK + H\(_2\)O
NH\(_4\)OH + HCL → NH\(_4\) + H\(_2\)O
NaOH + HCL → NaCL + H\(_2\)O
CH\(_3\)COOH + NaOH → CH\(_3\)COONa + H\(_2\)O
Enthalpy changes of neutralization are always negative - heat is released from the reaction of an acid and an alkali.
Such enthalpy changes are smaller in magnitude compared to that between the reaction of strong acids and strong bases.
Users' Answers & CommentsThe pollutant that is usually present in a city which generates its electricity from coal?
fog
carbon(ii)oxide
smog
sulphur(iv)oxide
Sulfur, due to the burning of coal in the process of generating electricity.
Users' Answers & CommentsThe dehydration of CH\(_3\)CH\(_2\)CH\(_2\)CH\(_2\)OH will give?
HC≡CCH\(_2\)CH\(_3\)
CH\(_2\)≡CH\(_2\)CH\(_3\)
CH\(_3\)C≡CCH\(_3\)
CH\(_3\)CH=CHCH\(_3\)
An alkene is produced when dehydration of alcohol is performed in which alcohol, upon reaction with protic acids, loses a molecule of water to form alkenes.
Such a reaction is an elimination reaction.
Users' Answers & CommentsWhen heat is absorbed during a chemical reaction, the reaction is said to be ___
thermodynamic
exothermic
isothermal
endothermic
An endothermic reaction is a chemical reaction in which heat is absorbed from its environment hence resulting in an increase in the enthalpy H of the system.
Users' Answers & CommentsWhich of the following best represents a solid gas mixture?
milk
kerosene
soil
smoke
Examples of solids in gas mixture:
- smoke
- ice clouds
- dust
Examples of liquid in gas mixture:
- fog
- mist
- vapour
- hair sprays
Examples of gas in solid mixture:
- aerogel
- styrofoam.