The latent heat of vapourisation of water at ${25}^{\circ }C$ is 10.5 kcal mol-1 and the standard heat of formation of liquid water is -68.3 kcal. The enthalpy change of the reaction

${H}_{2}\left(g\right)+\left(1/2\right){O}_{2}\left(g\right)\to {H}_{2}O\left(g\right)$ is therefore,

1. -57.8 kcal

2. -78.8 kcal

3. 78.8 kcal

4. -47.3 kcal

Concept Questions :-

Enthalpy and It's Type
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

Which of the following thermodynamic quantities is an outcome of the second law of thermodynamics ?

1. Work

2. Enthalpy

3. Internal energy

4. Entropy

Concept Questions :-

Spontaneity and Entropy
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

From the following data of $∆H$, of the following reactions,

What is the mole composition of the mixture of steam and oxygen on being passed over coke at 1273 K, keeping temperature constant.

1. 0.5 : 1

2. 0.6 : 1

3. 0.8 : 1

4. 1 : 1

Concept Questions :-

Enthalpy and It's Type
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

State which of the following statements is true ?

1. First law of thermodynamics is not adequate in predicting the direction of the process.

2. In an exothermic reaction, the total enthalpy of the products is greater than that of reactants.

3. The standard enthalpy of diamond is zero at 298 K and 1 atm pressure.

4. It is possible to calculate the value of $∆H$ for the reaction ${H}_{2}\left(g\right)+B{r}_{2}\left(l\right)\to 2HBr\left(g\right)$ from the bond enthalpy data.

Concept Questions :-

First Law of Thermodynamics
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

If $∆H$ of a reaction is 100 kJ mol-1, then the activation energy for forward reaction must be-

1. Greater than 100 kJ mol-1

2. Less than 100 kJ mol-1

3. Equal to 100 kJ mol-1

4. None is correct

Concept Questions :-

Enthalpy and It's Type
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

The intermediate SiH2 is formed in the thermal decomposition of silicon hydrides. Calculate $∆{H}_{f}^{\circ }$ of SiH2 given the following reactions

1. 353 kJ/mol

2. 321 kJ/mol

3. 198 kJ/mol

4. 274 kJ/mol

Concept Questions :-

Thermochemistry
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

A certain vessel X has water and nitrogen gas at a total pressure of 2 atm. and 300 K. All the contents of the vessel are transferred to another vessel Y having half the capacity of the vessel X. The pressiure of N2 in this vessel was 3.8 atm. at 300 K. The vessel Y is heated to 320 K and the total pressure observed was 4.32 atm. Calculate the enthalpy of vapourisation of water assuming it to be independent of temperature. Also assume the volume occupied by the gases in a vessel is equal to the volume of the vessel.

1. 39.637 kJ mol-1

2. 19.531 kJ mol-1

3. 396.37 kJ mol-1

4. 3.9127 kJ mol-1

Concept Questions :-

Enthalpy and It's Type
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

For a reaction,  is given by the equation  in the temperature range 300-600 K. The enthalpy of the reaction at 300 K -s -25.0 KJ. Calculate the enthalpy of the reaction at 450 K.

Also

1. -10.12 kJ

2. -28.32 kJ

3. -18.72 kJ

4. -8.21 kJ

Concept Questions :-

Enthalpy and It's Type
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

The heat of combustion of ethylene at ${17}^{\circ }C$ and at constant volume is -332.19 kcals. What is the value at constant pressure, given that water is in liquid state ?

1. -131.25 k cals

2. -412.23 k cals

3. -534.12 k cals

4. -333.35 k cals

Concept Questions :-

Enthalpy and It's Type
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

The enthalpies of the following reactions are shown alongwith.

Calculate the O-H bond energies for the hydroxyl radical.

1. 223.18 kJ mol-1

2. 423.38 kJ mol-1

3. 513.28 kJ mol-1

4. 113.38 kJ mol-1

Concept Questions :-

Thermochemistry