Chemistry 2017 Jamb Examination
Chemistry 2017 Jamb Examination
Question 11
For a general equation of the nature \( xP + yQ \rightarrow mR + nS \), the expression for the equilibrium constant is:
For a general reaction \( xP + yQ \rightarrow mR + nS \), the equilibrium constant \( K_c \) is given by the ratio of the product of the concentrations of the products raised to their stoichiometric coefficients to that of the reactants. \[ K_c = \dfrac{[R]^m [S]^n}{[P]^x [Q]^y} \]
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Question 12
A given mass of gas occupies 2 dm3 at 300 K. At what temperature will its volume be doubled, keeping the pressure constant?
Using Charles’ law: \[ \dfrac{V_1}{T_1} = \dfrac{V_2}{T_2} \] Given \( V_1 = 2 \; \text{dm}^3 \), \( T_1 = 300 \; \text{K} \), and \( V_2 = 4 \; \text{dm}^3 \). \[ \dfrac{2}{300} = \dfrac{4}{T_2} \]\[\Rightarrow T_2 = \dfrac{4 \times 300}{2} = 600 \; \text{K} \]
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Question 13
The oxidation number of iodine in KIO3 is:
Let the oxidation number of iodine be x. In KIO3:
+1 + x + 3(-2) = 0 → x - 5 = 0 → x = +5
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Question 14
An isomer of C5H12 is:
C5H12 has three isomers: n-pentane, 2-methylbutane, and 2,2-dimethylpropane (2-methylpropane). Hence, an isomer is 2–methylbutane.
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Question 15
When few drops of concentrated trioxonitrate(V) acid is added to an unknown sample and warmed, an intense yellow colouration is observed. The likely functional group present in the sample is:
An intense yellow colouration with concentrated trioxonitrate(V) acid indicates the presence of an aromatic amino group (–NH2) as seen in the xanthoproteic test for proteins. Thus, the compound contains NH2RCHCOOH group.
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Question 16
A sample of orange juice is found to have a pH of 3.80. What is the concentration of the hydroxide ion in the juice?
Given \( \text{pH} = 3.80 \), so: \[ \text{pOH} = 14 - 3.80 = 10.20 \] \[ [OH^-] = 10^{-\text{pOH}} \]\[= 10^{-10.2} = 6.3 \times 10^{-11} \]
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Question 17
Incomplete oxidation of ethanol yields:
Ethanol \( (CH_3CH_2OH) \) undergoes incomplete oxidation to form ethanal \( (CH_3CHO) \). Complete oxidation yields ethanoic acid \( (CH_3COOH) \).
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Question 18
The salt formed from a weak acid and a strong base hydrolyzes in water to form:
A salt of a weak acid and strong base (e.g., sodium acetate) hydrolyzes to produce an alkaline solution because the anion reacts with water to form OH− ions.
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Question 19
The ideal gas laws and equations are true for all gases at:
Real gases behave ideally when the intermolecular forces are negligible, which occurs at low pressure and high temperature.
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Question 20
When \( \Delta H \) is negative, a reaction is said to be:
A negative \( \Delta H \) indicates that heat is released to the surroundings, hence the reaction is exothermic.
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