Heat of Formation

Q. 44 At a certain temperature only 50% of HI is dissociated into H2 and I2 at equlibrium. The equilibrium constant is A 1 B 3 C 0.5 D 0.25

Q. The mass of CaCO3 required to react completely with 20 mL of 1.0 M HCL as per the reaction CaCO3+2HCl-->CaCl2+CO2+H2O

Q.

The enthalpy of formation of methane at constant pressure and $300K$ is $-75.83KJ$. What will be the heat of formation at constant volume? $(R=8.3J{K}^{-1}mo{l}^{-1}$)

1. 73.34 kJ

2. 72.34 kJ

3. -72.34 kJ

4. -73.34 kJ

Q.

What will be the resultant pH when 200mL of an aqueous solution of HCl (pH = 2.0) is mixed with 300mL of an aqueous solution of NaOH (pH = 12.0) ?​

1. 8.8

2. 11.3

3. 3.5

4. 2.69

Q.

The correct order of the thermal stability of hydrogen halides (H -X) is

1. HI>HBr>HCl>HF

2. HF>HCl>HBr>HI

3. HI>HCl<HF<HBr

4. HCl<HF<HBr<HI

Q. 1)The value of Kp for the reaction CO2 +C <=> 2CO is 3 at 1000 K. If initially pCO2=0.48 bar and pCO=0bar and pure graphite is present, calculate the equilibrium partial pressure of CO and CO2. 2) The ionization constant of HF is 3.2*10^(-4). Calculate the degree of dissociation of HF in its 0.02M solution. Calculate the concentration of all species present (H30+, F, HF) in the solution and its pH. Do we have to multiply the initial concentration of the reactant to the degree of dissociation of equilibrium concentration of reactant and product?

Q. For which of the following substances, the enthalpy of atomization also represents the enthalpy of sublimation?

1. $C_{12}{H}_{22}{O}_{11}$
2. $KCl$
3. $Na$
4. $RbOH$

Q. The standard E.M.F of the cell written as
$Cd\left(Hg\right)|CdS{O}_4.\frac{8}{3}{H}_{2}O\left(s\right)||CdS{O}_4(sat.)|H{g}_{2}S{O}_4\left(s\right)|Hg$ in which the cell reaction is
$Cd\left(Hg\right)+H{g}_{2}S{O}_4\left(s\right)+\frac{8}{3}{H}_{2}O\left(l\right)\rightleftharpoons CdS{O}_4.\frac{8}{3}{H}_{2}O\left(s\right)+2Hg\left(l\right)$ is $1.0185V$ at ${25}^{o}C$. Calculate $\Delta S^o$ for the cell reaction if ${\left(\frac{\partial E^o}{\partial T}\right)}_P$ for the cell is $5.00\times {10}^{-5}V{K}^{-1}$
Take, $F=96485Cmo{l}^{-1}$

1. $32.6J{K}^{-1}$
2. $12.5kJ{K}^{-1}$
3. $9.65J{K}^{-1}$
4. $8kJ{K}^{-1}$

Q. The heat of transition ($\Delta H_t$) of graphite into diamond would be,
where, $C\left(graphite\right)+O_2\left(g\right)\to C{O}_2\left(g\right)$ $\Delta H=xkJ$
$C\left(diamond\right)+O_2\left(g\right)\to C{O}_2\left(g\right)$ $\Delta H=ykJ$

1. $x+y$ kJ/mole
2. $x-y$ kJ/mole
3. $y-x$ kJ/mole
4. None of these

Q. If 2/9 of 1 mole of HI is dissociates, the equilibrium constant of disintegration of acid at same temperature will be? How to solve

Q.

Which of the following has largest size

1. Al

2. Al⁺

3. Al⁺²

4. Al⁺³

Q.

How much heat will be required at constant pressure to form $1.28kg$ of $Ca{C}_2$ from $CaO\left(s\right)$ and $C\left(s\right)$?

Given:

${\Delta }_r{H}^0(CaO,s)=-152kcal/mol$.

${\Delta }_r{H}^0(Ca{C}_2,s)=-14kcal/mol$.

${\Delta }_r{H}^0(CO,g)=-26kcal/mol$.

1. 3840 kcal

2. 2240 kcal

3. 22.4 kcal

4. 224 kcal

Q. 12.6g of impure Na2CO3 is treated with 500ml of 0.5m HCL for complete reaction .the remaining HCL is back titrated by adding 100ml of 0.5 M NaOH .calculate the percentage purity of Na2CO3

Q. 3.2 moles of HI were cheated in a sealed bulb at 444 degree celcius fill the equilibrium was reached.Its degree of dissociation was found to be 20 percent calculate the number of moles of hydrogen iodide hydrogen and iodine present at equilibrium point and determine the value of equilibrium constant for the fraction 2HI gives H2 +I2 consider the volume of the container 1L

Q. 40. Consider the reaction CaCO3+2HCL (l) ~》CaCl2+CO2+H2O (l).what mass of CaCO3 is required to react with 20mL 1M HCL?

Q. Standard molar enthalpy of formation of $C{O}_2$ is equal to

1. Zero
2. The standard molar enthalpy of combustion of gaseous carbon
3. The sum of standard molar enthalpies of formation of CO and $O_2$
4. The standard molar enthalpy of combustion of carbon (graphite)

Q.

The enthalpy of formation of methane at constant pressure and $300K$ is $-75.83KJ$. What will be the heat of formation at constant volume? $(R=8.3J{K}^{-1}mo{l}^{-1}$)

1. -73.34 kJ

2. 73.34 kJ

3. 72.34 kJ

4. -72.34 kJ

Q. The standard molar heat of formation of ethane , carbon dioxide and liquid water are -21.1 , -94.1 , and -68.3 kcal respectively. Calculate the standard molar heat of combustion of ethene.

Q. What is stark effect?

Q. 64 The correct decreasing order of magnitude of enthalpy of hydrogenation is And on what factor enthalpy of hydrogenation depends upon

Q. Draw the resonance structures for $C{H}_{3}CH=CHCHO$. Also, show the electron shift using curved-arrow notation.

Q. ASSERTION:
${\Delta }_f{H}^o$ for white phosphorus has been taken to be zero, whereas black phosphorus is the most stable allotrope of phosphorus and this is the only exception.

REASON:
The reference standard state of white phosphorus is taken despite the fact that this form is not the most stable allotrope but simply the most reproducible form of phosphorus.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Assertion incorrect but Reason is correct

Q. Which of the following substances do not have standard enthalpy of formation as zero?

1. $Ca\left(s\right)$
2. $Hg\left(l\right)$
3. $O_2\left(g\right)$
4. $C{O}_2\left(g\right)$

Q. How many moles of H2SO4 should be removed from 10L solution so that pH changes from 2 to 3

Q. 1)The value of Kp for the reaction CO2 +C <=> 2CO is 3 at 1000 K. If initially pCO2=0.48 bar and pCO=0bar and pure graphite is present, calculate the equilibrium partial pressure of CO and CO2. 2) The ionization constant of HF is 3.2*10^(-4). Calculate the degree of dissociation of HF in its 0.02M solution. Calculate the concentration of all species present (H30+, F, HF) in the solution and its pH. Do we have to multiply the initial concentration of the reactant to the degree of dissociation of equilibrium concentration of reactant and product?

Q. The enthalpy of hydrogenation of cyclohexene is $-119.5kJ/mol$. If resonance energy of benzene is $-150.4kJ/mol$ then its enthalpy of hydrogenation would be:

1. $-269.9kJ/mol$
2. $-358.5kJ/mol$
3. $-508.9kJ/mol$
4. $-208.1kJ/mol$

Q. Which of the following equations represent the standard heat of formation of $C_2{H}_4$?

1. $2C\text{(diamond)}+2H_2\left(g\right)\to C_2{H}_4\left(g\right)$
2. $2C\text{(graphite)}+2H_2\left(g\right)\to C_2{H}_4\left(g\right)$
3. $2C\text{(diamond)}+4H\left(g\right)\to C_2{H}_4\left(g\right)$
4. $2C\text{(graphite)}+4H\left(g\right)\to C_2{H}_4\left(g\right)$

Q. The solubility of alkali metal salts in water is due to the fact that the cations get hydrated by water molecules. The degree of hydration depends upon the size of the cation. If the trend of relative ionic radii is $C{s}^{+}>R{b}^{+}>K^{+}>N{a}^{+}>L{i}^{+}$.
What is the relative degree of hydration?

1. $C{s}_{\left(aq\right)}^{+}>R{b}_{\left(aq\right)}^{+}>K_{\left(aq\right)}^{+}>N{a}_{\left(aq\right)}^{+}>L{i}_{\left(aq\right)}^{+}$
2. $L{i}_{\left(aq\right)}^{+}>N{a}_{\left(aq\right)}^{+}>K_{\left(aq\right)}^{+}>R{b}_{\left(aq\right)}^{+}>C{s}_{\left(aq\right)}^{+}$
3. $N{a}_{\left(aq\right)}^{+}>K_{\left(aq\right)}^{+}>R{b}_{\left(aq\right)}^{+}>C{s}_{\left(aq\right)}^{+}>L{i}_{\left(aq\right)}^{+}$
4. $C{s}_{\left(aq\right)}^{+}>N{a}_{\left(aq\right)}^{+}>L{i}_{\left(aq\right)}^{+}>K_{\left(aq\right)}^{+}>R{b}_{\left(aq\right)}^{+}$

Q.

In a chemical reaction, the energy required to dissociate 4g of H₂ into free gaseous atoms is x KJ. What will be the value of ∆H_H-H?

1. x/2 kJ mol^-1

2. 0.25 x kJ mol^-1

3. x/3 kJ mol^-1

4. x kJ mol^-1

Q. In the reaction $C{S}_2\left(l\right)+3O_2\left(g\right)\to C{O}_2\left(g\right)+2S{O}_2\left(g\right)△H=-265kcal$
The enthalpies of formation of $C{O}_2$ and $S{O}_2$ are both negative and are in the ratio 4 : 3. The enthalpy of formation of $C{S}_2$ is + 26 kcal/mol. Calculate the enthalpy of formation of $S{O}_2.$

1. - 90 kcal/mol
2. -52 kcal/mol
3. -78 kcal/mol
4. -71.7 kcal/mol