Learn more about the properties, composition, and structure of substances (elements and compounds) with these Chemistry questions and answers. This Test can be used by students preparing for Chemistry in JAMB, WAEC, NECO or Post UTME.
A reaction takes places spontaneously if?
∆G = O
∆S < O and ∆H > O
∆H < T ∆S
∆G > O
Correct answer is C
No explanation has been provided for this answer.
The oxidation states of chlorine in HOCL, HCLO3 and HCLO4 are respectively?
-1, +5, and +7
-1, -5 and 7
+1, +3 and +4
+1, +5 and +7
Correct answer is D
No explanation has been provided for this answer.
OH- - e → OH
CIsup>- - e → CI
OHsup>- + CIsup>-HCI + O2
Na+ - esup>- Hg (Na)/(Hg) amalgam
Correct answer is A
No explanation has been provided for this answer.
1
2
3
4
Correct answer is B
Ampere = (Coulomb) x (Sec) x 1930 secs = 965 coulombs (unit of current)
But quantity of electricity = current x time = (Coulomb)/(Sec) x time
If 0.5 A for 32 mins 10 secs; Quantity of electricity = (0.5 coulomb)/(Sec x 1930) secs
= 965 coulombs
Since 965 coulombs give 0.325 g M
i.e1 coulombs = (0.325)/(965) g
∴96500 coulombs = (0.30)/(965) x 96500 =32.5 g
∴(65 g)/(32.5) = 2
inference: it takes 2 Faraday of electricity to deposit 1 mole of M. Therefore, the change on M ion = 2.
4.0 g of sodium hydroxide in 250 cm3 of solution contains?
0.40 moles per dm3
0.10 moles per dm3
0.04 moles per dm3
0.02 moles per dm3
Correct answer is A
Unit of concentration = (moles)/(dm3)
If 250 cm3 solution NaOH contains 4.0 g NaOH
i.e -1cm3 solution NaOH (4.0)/(250) g
∴ 1000 cm3 (1 dm3) will contain (40 x 1000) / (250 x 1) = 16 g/dm3
16 g/dm3 = 16g/dm3 + molar mass NaOH
because no of moles = (mass of substance given) / (molar mass)
∴ (16 g) / (40 g) dm3 = (16 g)/(dm3 x (1 mole)/ (40g) = 0.4 (moles)/(dm3)