Heat of Reaction

Q.

Define enthalpy of combustion.

Q. How do you determine the sign of (delta) s and (delta ) h?

Q. Calculate the molality of ethanol in water in which the mole fraction of ethnol is $0.040$.

1. $2.315m$
2. $1.315m$
3. $3.315m$
4. $4.315m$

Q.

power company burns approximately 475 tons of coal per day to produce electricity if the sulphur content of the coal is 1. 2 percentage by weight how many tone SO_{​​​​​2} are dumped into the atmosphere each day?

Q.

Calculate the amount of carbon dioxide gas and calcium oxide (quicklime) formed during the decomposition of 25g of calcium carbonate(limestone)

Q.

During complete combustion of one mole of butane, 2658 kJ of heat is released. The thermochemical reaction for above change is
(a) $2C_4{H}_{10}\left(g\right)+13O_2\left(g\right)\to 8C{O}_2\left(g\right)+10H_{2}O\left(l\right);{\Delta }_{c}H=-2658.0kJmo{l}^{-1}$
(b) $C_4{H}_{10}\left(g\right)+\frac{13}{2}{O}_2\left(g\right)\to 4C{O}_2\left(g\right)+5H_{2}O\left(l\right);{\Delta }_{c}H=-1329.0kJmo{l}^{-1}$
(c) $C_4{H}_{10}\left(g\right)+\frac{13}{2}{O}_2\left(g\right)\to 4C{O}_2\left(g\right)+5H_{2}O\left(l\right);{\Delta }_{c}H=-2658.0kJmo{l}^{-1}$
(d) $C_4{H}_{10}\left(g\right)+\frac{13}{2}{O}_2\left(g\right)\to 4C{O}_2\left(g\right)+5H_{2}O\left(l\right);{\Delta }_{c}H=+2658.0kJmo{l}^{-1}$

Q. 25. For a reversible reaction where N2O4 converts to NO2 , the rate of disappearance of NO2 will be 1.K1[N204]-k2[N02]2 2. 2K1[N204]-2k2[N02]2 3. K2[N02]2-k1[N204] 4. 2K2[NO2]2-2k1[N204]

Q.

For the formation of $3.65\mathrm{g}$ $\mathrm{HCl}$ gas. What volume of hydrogen gas and chlorine at $\mathrm{STP}$ are required?

Q. Calculate the resonance energy of $N_{2}O$ from the following data:
${△}_f{H}^{o}of{N}_{2}O=82kJmo{l}^{-1},$
$N\equiv N,946kJmo{l}^{-1};N=N,418kJmo{l}^{-1};$
$O=O,498kJmo{l}^{-1};N=O,607kJmo{l}^{-1}$

1. $-88kJmo{l}^{-1}$
2. $78kJmo{l}^{-1}$
3. $98kJmo{l}^{-1}$
4. $-78kJmo{l}^{-1}$

Q.

How can one define the internal energy of a system?

Q. The total vapour pressure of a mixture of 1 mole of A(partial pressure = 200) and 3 mole of B(partial pressure = 360) is 350 mm Hg. Then this is positive deviation or negative deviation

Q.

The reaction of cyanamide, $N{H}_{2}C{N}_{\left(s\right)}$, with dioxygen was carried out in a bomb calorimeter, and $\Delta U$ was found to be $-742.7kJmo{l}^{-1}$ at 298 K. calculate enthalpy change for the reaction at 298 K.
$N{H}_{2}C{N}_{\left(g\right)}+\frac{3}{2}{O}_{2\left(g\right)}\to N_{2\left(g\right)}+C{O}_{2\left(g\right)}+H_2{O}_{\left(l\right)}$

Q. Given that:
$C\left(graphite\right)+O_2\left(g\right)\to C{O}_2\left(g\right)\Delta H=xkJmo{l}^{-1}$

$C\left(graphite\right)+\frac{1}{2}{O}_2\left(g\right)\to C{O}_2\left(g\right)\Delta H=ykJmo{l}^{-1}$

$CO\left(g\right)+\frac{1}{2}{O}_2\left(g\right)\to C{O}_2\left(g\right)\Delta H=zkJmo{l}^{-1}$
Based on the given thermochemical equations, find out which one of the following algebric relationships is correct?

1. $2z=x-y$
2. $z=x-y$
3. $z=x+y$
4. $z=x+2y$

Q. The increase in internal energy of 1 kg of water at ${100}^{0}C$ when it is converted into steam at the same temperture and at 1 atm (100 kPa) will be:
(The density of water and steam are $1000kg/m^3$ and $0.6kg/m^3$ respectively. The latent heat of vapourisation of water is 2.25 ${10}^6$ J/kg.)

1. $2.08\times {10}^{6}J$
2. $4\times {10}^{7}J$
3. $3.27\times {10}^{8}J$
4. $5\times {10}^{9}J$

Q.

An organic compound A on heating with concentrated ${\mathrm{H}}_2{\mathrm{SO}}_4$ forms a compound B which on addition of one mole of hydrogen in presence of $\mathrm{Ni}$ forms a compound C. One mole of compound C on combustion forms two moles of ${\mathrm{CO}}_2$ and $3$ moles of ${\mathrm{H}}_2\mathrm{O}$. Identify the compounds A, B and C and write the chemical equations of the reactions involved.

Q.

What do you understand by exothermic reaction and endothermic reaction? Give one example of each type.

Q.

18.0 g of water completely vaporises at ${100}^{\circ }C$ and 1 bar pressure and the enthalpy change in the process is 40.79 kJ $mo{l}^{-1}$. What will be the enthalpy change for vaporising two moles of water under the same conditions? What is the standard enthalpy of vaporisation for water?

Q. Energy required to dissociate 4 g of gaseous hydrogen into free gaseous atoms is 208 Kcal at ${25}^{\circ }C$. The bond energy of H-H bond per mole will be

1. 104 K cal
2. 10.4 K cal
3. 1040 K cal
4. 104.2 k cal

Q. The variation of heat of reaction with temperature is given by:

1. Van't Hoff equation
2. Clausius-Clapeyron equation
3. Kirchoff's equation
4. Nernst equation

Q. $17.0g$ of $N{H}_3$ completely vapourises at $-{33.42}^{o}C$ and $1$ bar pressure and the enthalpy change in the process is $23.4kJ{\text{mol}}^{-1}$. The enthalpy change for the vapourisation of $85g$ of $N{H}_3$ under the same conditions is $kJ$

Q. Which equation do not represent enthalpy change of reaction which correspond to the standard enthalpy change of atomisation of chlorine?

1. $\frac{1}{2}C{l}_2\left(g\right)\to Cl\left(g\right)$
2. $\frac{1}{2}C{l}_2\left(l\right)\to Cl\left(g\right)$
3. $C{l}_2\left(g\right)\to 2Cl\left(g\right)$
4. $C{l}_2\left(l\right)\to 2Cl\left(g\right)$

Q. Ethylene reacts with Baeyer’s reagent to give

1. glycol
2. ethyl alcohol
3. acetaldehyde
4. oxalic acid

Q. When an ideal gas is compressed adiabatically and reversibly, the final temperature is 1- higher than the initial temperature 2- lower than the initial temperature 3- same as the initial temperature 4- dependent on rate of compression

Q. For the gas-phase decomposition
$PC{l}_5\left(g\right)\stackrel{△}{\rightleftharpoons }PC{l}_3\left(g\right)+C{l}_2\left(g\right):$

1. $△H<0,△S<0$
2. $△H>0,△S>0$
3. $△H>0,△S<0$
4. $△H<0,△S>0$

Q.

In an exothermic reaction, heat is evolved, and system loses heat to the surrounding. For such system
(a) $q_p$ will be negative
(b) ${\Delta }_{r}H$ will be negative
(c) $q_p$ will be positive
(d) ${\Delta }_{r}H$ will be positive

Q. What is the mole fraction of glycerin $C_3{H}_5(OH{)}_3$ in a 100 g solution containing 33 g of glycerin, 60 g isopropyl alcohol and rest water?

1. 0.359
2. 0.258
3. 0.205
4. 0.480

Q. The specific heats of iodine vapour and solid are $0.031$ and $0.055cal{K}^{-1}{g}^{-1}$ respectively. If heat of sublimation of iodine is $24cal{g}^{-1}$ at ${200}^{o}C$, find its value at ${250}^{\circ }C$.

1. $5.7cal{g}^{-1}$
2. $11.4cal{g}^{-1}$
3. $22.8cal{g}^{-1}$
4. $45.6cal{g}^{-1}$

Q.

The molar enthalpy of vaporisation of acetone is less than that of water. Why?

Q.

How much energy does it take to break a hydrogen bond?

Q.

If the heats of combustion of ethane, hydrogen, and graphite are $-1560,-393.5,\mathrm{and}-286\mathrm{kJ}/\mathrm{mol}$, respectively, the standard heat of production ${}_{\mathrm{f}}{\mathrm{H}}_{298°}$ of ethane $(\mathrm{in}\mathrm{kJ}/\mathrm{mol})$ is