Enthalpy | MCQs

Explanation

Enthalpy is a form of energy, so its SI unit is Joule (J).

1 calorie = 4.184 joules.

But Joule is the standard unit in thermodynamics.

Explanation

Standard enthalpy change is measured at a defined pressure of 101 kPa (or 1 bar, according to Testbook.com) and a temperature of 298 K (25°C). 

Explanation

Explanation

It is the total heat content of a system when the pressure is constant.

It helps us understand energy changes in chemical reactions.

Explanation

The reaction NaOH + HCl → NaCl + H₂O is a neutralization reaction between a strong base and a strong acid.

The enthalpy change in such reactions is called the heat of neutralization.

Explanation

Use the Gibbs free energy equation:

$$\Delta G=\Delta H-T\Delta S$$

For a process to be spontaneous, $Delta G < 0$

• If $Delta H < 0$ (exothermic)

• And $Delta S > 0$ (entropy increases)

• Then:

  $$\Delta G=\text{negative}-T\times \text{positive}=\text{always negative}$$

 So, no matter the temperature, $Delta G$ will be negative ⇒ spontaneous at all temperatures

Explanation

Explanation

Enthalpy of neutralization is the enthalpy change when 1 mole of water is formed by the reaction of an acid with an alkali under standard conditions.

It typically releases energy as heat during the neutralization process.