Enthalpy and Enthalpy Change

Consider the following reactions

(i) ${\text{H}}_{\left(\text{aq}\right)}^{+}+{\text{OH}}_{\left(\text{aq}\right)}^{-}\to {\text{H}}_2\text{O}\left(\mathrm{\ell \; }\right)$

$\Delta \text{H}=-{\text{X}}_1{\text{ k J mol}}^{-1}$

(ii) ${\text{H}}_2\left(\text{g}\right)+\frac{1}{2}{\text{O}}_2\left(\text{g}\right)\to {\text{H}}_2\text{O}\left(\ell \right)$

$\Delta \text{H}=-{\text{X}}_2{\text{ k J mol}}^{-1}$

(iii) ${\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)\to \mathrm{CO}\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

$\Delta \text{H}=-{\text{X}}_3{\text{ k J mol}}^{-1}$

(iv) ${\text{C}}_2{\text{H}}_2\left(\text{g}\right)+\frac{5}{2}{\text{O}}_2\left(\text{g}\right)\to 2{\text{CO}}_2\left(\text{g}\right)+{\text{H}}_2\text{O}\left(\ell \right)$

$\Delta \text{H}=+4{\text{X}}_4{\text{ k J mol}}^{-1}$

Enthalpy of formation of ${\text{H}}_2\text{O}\left(\ell \right)$

Exaplain the enthalpy change in solids and liquids.

The enthalpy change of a reaction is independent of

The quantity of heat (in $J$) required to raise the temperature of $1.0\mathit{ }kg$ of ethanol from $293.45 K$ to the boiling point and then change the liquid to vapor at that temperature is closest to [Given, boiling point of ethanol $351.45 K$. Specific heat capacity of liquid ethanol $2.44\mathit{ }J\mathit{ }{g}^{-1} K^{-1}$. Latent heat of vaporisation of ethanol $855 J{g}^{-1}$ ]

When a process takes place at constant volume, the heat absorbed or released is equal to the Enthalpy change.

Define 'Enthalpy'

The difference between $\mathrm{Cp}$ and $\mathrm{Cv}$ for liquids and solids is extremely large.

Derive the relation between $∆\mathrm{H}$ and $∆\mathrm{U}$ for an ideal gas. Explain each term involved in the equation.

One mol of a non-ideal gas undergoes a change of state $(2.0 \mathrm{atm}, 3.0 \mathrm{L}, 95 \mathrm{K}) \to (4.0 \mathrm{atm}, 5.0 \mathrm{L}, 245 \mathrm{K})$ with a change in internal energy, $∆\mathrm{U}$$= 30.0 \mathrm{L} \mathrm{atm}$. The change in enthalpy $(∆\mathrm{H})$ of the process in $\mathrm{L} \mathrm{atm}$ is

Molar heat capacity of aluminium is $25$ $\mathrm{J} {\mathrm{K}}^{-1} {\mathrm{mol}}^{-1}$. The heat necessary to raise the temperature of $54 \mathrm{g}$ of aluminium (Atomic mass $27 \mathrm{g} {\mathrm{mol}}^{-1}$ ) from $30 °\mathrm{C}$ to $50°\mathrm{C}$ is

The enthalpy change for the reaction ${\mathrm{C}}_2{\mathrm{H}}_4 \left(\mathrm{g}\right) + {\mathrm{H}}_2 \left(\mathrm{g}\right) \to {\mathrm{C}}_2{\mathrm{H}}_6 \left(\mathrm{g}\right) \mathrm{is} - 620 \mathrm{J}$ when $100 \mathrm{mL}$ of ethylene and $100 \mathrm{mL}$ of$H_2$ react at$1$atm pressure. Calculate the pressure volume work and $∆\mathrm{U}$.

What are the signs of $∆\mathrm{S}$ and $∆\mathrm{H}$ for the following reaction? Explain with reasons.

$2\mathrm{H}\left(\mathrm{g}\right) \to {\mathrm{H}}_2\left(\mathrm{g}\right)$

Define enthalpy. At constant pressure show that $△\mathrm{H} = △\mathrm{U} + \mathrm{P}.△\mathrm{V}$.

The heat evolved in a reaction of $7.5 \mathrm{g}$ of ${\mathrm{Fe}}_2{\mathrm{O}}_3$ with enough $\mathrm{CO}$ is $1.164 \mathrm{kJ}$. Calculate $△\mathrm{H}°$ for the reaction ${\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right) + 3\mathrm{CO}\left(\mathrm{g}\right) \to 2\mathrm{Fe}\left(\mathrm{s}\right) + 3{\mathrm{CO}}_2\left(\mathrm{g}\right)$
 

Arrange in order of increasing enthalpy ${\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right), {\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right), {\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$.

If $20\mathrm{ }\mathrm{mL}$ of $\mathrm{HCl}$ is added to $20\mathrm{ }\mathrm{mL}$ of $\mathrm{NaOH}$ solution of same strength, $5°\mathrm{C}$ increment in temperature takes place. If $200$ $\mathrm{mL}$ of same $\mathrm{HCl}$ solution is mixed with $200\mathrm{ }\mathrm{mL}$ of same $\mathrm{NaOH}$ solution, temperature increases by-

Using the following data, calculate the amount of heat evolved during the complete combustion of 100ml of liquid benzene.

(i) $18 \mathrm{g}$ graphite, on complete combustion, evolves $590 \mathrm{kJ}$ heat.
(ii)$15889 \mathrm{kJ}$ of heat is required to dissociate all the molecules of $1 \mathrm{L}$ liquid water into ${\mathrm{H}}_2\mathrm{ }$ and ${\mathrm{O}}_2$ .
(iii) The heat of formation of liquid benzene is $+50$ $\mathrm{kJ}/\mathrm{mol}$ .
(iv) Density of ${\mathrm{C}}_6{\mathrm{H}}_6\left(\mathrm{l}\right)\mathrm{ }=\mathrm{ }0.87\mathrm{g}/\mathrm{mL}$ and that of ${\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)=1\mathrm{g}/\mathrm{mL}$

(all energies measured at standard condition)

Given $∆{\mathrm{H}}_{\mathrm{f}}^0$ of ${\mathrm{N}}_2\mathrm{O}=82$ . (All data at standard state in $\mathrm{kJ}/\mathrm{mol}$ ).
Bond energies of
$\mathrm{N}\equiv \mathrm{N}$     $946$
$\mathrm{N}=\mathrm{N} \mathrm{ }$ $418$
$\mathrm{O}=\mathrm{O}$     $498$
$\mathrm{N}=\mathrm{O}$      $607$

Then calculate the resonance energy of ${\mathrm{N}}_2\mathrm{O}$