Select the correct option based on statements given below:
Assertion (A): Combustion of all organic compounds is an exothermic reaction.
Reason (R): The enthalpies of all elements in their standard state are zero.
 
1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. (A) is false but (R) is true.
Subtopic:  Thermochemistry |
 77%
From NCERT
To view explanation, please take trial in the course.
NEET 2023 - Target Batch - Aryan Raj Singh
Hints
To view explanation, please take trial in the course.
NEET 2023 - Target Batch - Aryan Raj Singh

On the basis of thermochemical equations (i), (ii), and (iii), find out which of the algebraic relationships given in options (a) to (d) is correct:

(i). C(graphite) + O2(g) → CO2 (g) ; ∆rH = x kJmol-1
(ii). C(graphite) + \(\frac{1}{2}\)O2(g) → CO(g) ; ∆rH = y kJ mol-1
(iii). CO(g) + \(\frac{1}{2}\)O2(g) → CO2(g); ∆rH = z kJ mol-1

1. z=x+y

2. x=y-z

3. x=y+z

4. y=2z-x

Subtopic:  Thermochemistry |
 76%
From NCERT
To view explanation, please take trial in the course.
NEET 2023 - Target Batch - Aryan Raj Singh
Hints
To view explanation, please take trial in the course.
NEET 2023 - Target Batch - Aryan Raj Singh

The enthalpies of elements in their standard states are taken as zero. The enthalpy of formation of a compound is-

1. Generally negative 2. Always positive
3. Zero 4. Never negative
Subtopic:  Thermochemistry |
 54%
From NCERT
To view explanation, please take trial in the course.
NEET 2023 - Target Batch - Aryan Raj Singh
Hints
To view explanation, please take trial in the course.
NEET 2023 - Target Batch - Aryan Raj Singh

The enthalpy of sublimation of a substance is equal to-

1. Enthalpy of fusion + Enthalpy of vaporisation

2. Enthalpy of fusion

3. Enthalpy of vaporisation

4.  Twice the enthalpy of vaporisation

Subtopic:  Thermochemistry |
 86%
From NCERT
To view explanation, please take trial in the course.
NEET 2023 - Target Batch - Aryan Raj Singh
Hints
To view explanation, please take trial in the course.
NEET 2023 - Target Batch - Aryan Raj Singh