Energy changes - Jamb Chemistry Past Questions and Answers

Question 31:

• JAMB 1993

For iodine crystals to sublime on heating, the molecules must acquire energy that is?

A. Less than the forces odf attraction in the solid
B. Equal to the forces of attraction in th solid
C. Necessary to melt the solid
D. Greater than the forces of attraction in both the solid and the liquid phases

Question 32:

• JAMB 1993

A reaction takes places spontaneously if?

A. ∆G = O
B. ∆S < O and ∆H > O
C. ∆H < T ∆S
D. ∆G > O

Question 33:

• JAMB 1993

The standard enthalpies of formation of CO_2(g), H₂O(g) and CO_(g) in kJ mol^- are -394, -242 and -110 respectively. What is the standard enthalpy change for the reaction CO_(g) + H_2(g)O → CO_2(g) + H_2(g)?

A. -42 KJ mol^-
B. +42 KJ mol^-
C. -262 KJ mol^-
D. +262 KJ mol^-

Question 34:

• JAMB 1993

Palm wine turns sour with time because?

A. The sugar content is converted into alcohol
B. The carbon (IV) oxide formed during the fermentation process has a sour taste
C. It is commonly adulterated by the tappers and sellers
D. Microbial activity results in the production of orgain acids within it

Question 35:

• JAMB 1994

The ∆H for the reaction represented by the energy profile above is

A. -100 kJ mol-^-1
B. + 100 kJ mol^-1
C. +50 kJ mol^-1
D. -50 kJ mol^-1