Tag: chemistry

Questions Related to chemistry

Use the following data to calculate second electron ainity of oxygen, i.e., for the process
$O^{-}(g) + e^{-}(g)  \rightarrow O^{2-}(g)$
Is the $O^{2-}$ ion stable in the gas phase?.Why is it stable in solid MgO?
Heat of sublimation of $Mg(s) = + 147.7 kJ mol^{-1}$
Ionisation energy of Mg(g) to form
$Mg^{2+}(g) = + 2189.0 kJ mol^{-1}$
Bond dissociation energy for $O _2 = + 498.4 kJmol^{-1}$
First electron affinity of $O(g) = - 141.0 kJ mol^{-1}$
Heat formation of $MgO(s) = -601.7 kJ mol^{-1}$
Lattice energy of $MgO = -3791.0 kJ mol^{-1}$

chemistry lattice energy born-haber cycle born-haber cycles energy cycles

  1. 601.7

  2. 744.4

  3. 1346.1

  4. 147.7

Show answer
Correct Option: B
Explanation:

Option (B) is correct.

$\triangle H _1=-1346.1+q\ Mg(s)+\frac { 1 }{ 2 } O _{ 2 }(g)\rightarrow MgO(s)\ \triangle H _{ 2 }=-601.7\ By\quad Born-Haber\quad Cycle(based\quad on\quad Hess\quad law)\ \triangle H _{ 1 }=\triangle H _{ 2 }\ -1346.1+q=-601.7\ \qquad \qquad q=744.4kJ\quad mol^{-1}$

Select correct statement.

chemistry lattice energy born-haber cycle born-haber cycles energy cycles

  1. Both lattice energy and hydration energies decrease with ionic size.

  2. Lattice energy can be calculated using Born-Haber cycle.

  3. If the anion is larger compared to the cation, the lattice energy will remain almost constant within a particular group.

  4. All the above are correct statements.

Show answer
Correct Option: D
Explanation:

All the given statements are correct.
(A) Both lattice energy and hydration energies decrease with ionic size With large size, the charge is more dispersed. hence, the extent of hydration is smaller. Also the packing is inefficient.
(B) Lattice energy can be calculated using Born-Haber cycle The BornHaber cycle is an approach to analyze reaction energies. The cycle is concerned with the formation of an ionic compound from the reaction of a metal  (often a Group I or Group II element) with a halogen.
(C) If the anion is larger compared to the cation, the lattice energy will remain almost constant within a particular group

Caesium chloride is formed according to the following equation:

$Cs(s)+0.5{Cl} _{2}(g)\longrightarrow CsCl(s)$

The enthalpy of sublimation of $Cs$, enthalpy of dissociation of chlorine, ionization energy of $Cs$ and electron affinity of chlorine are $81.2, 243.0, 375.7$ and $-348.3kJ$ ${ol}^{-1}$. The energy change involved in the formation of $CsCl$ is $388.6\ kJ.{mol}^{-1}$. Calculate the lattice energy of $CsCl$.

chemistry lattice energy born-haber cycle born-haber cycles energy cycles

  1. $-618.7\ kJ{mol}^{-1}$

  2. $+618.7\ kJ{mol}^{-1}$

  3. $1315.2\ kJ{mol}^{-1}$

  4. None of these

Show answer
Correct Option: A

The ionization potential of ithium is 520 KJ/ mole .The energy required to convert 70 mg of lithum atoms in gaseous state into $Li^{+}$ ions is ______________.

chemistry lattice energy born-haber cycle born-haber cycles energy cycles

  1. 52 KJ

  2. 5.2 KJ

  3. 520 KJ

  4. 52 J

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Correct Option: B

The atoms of hydrogen combine to form a molecule of hydrogen gas, the energy of the $H _2$ molecule is:

chemistry lattice energy born-haber cycle born-haber cycles energy cycles

  1. Greater than that of seperate atoms

  2. Equal to that of seperate atoms

  3. Lower than that of seperate atoms

  4. Some times lower and some times higher

Show answer
Correct Option: C

Which of the following bonds has the highest bond energy?

chemistry lattice energy born-haber cycle born-haber cycles energy cycles

  1. Si-Si

  2. Si=Si

  3. Si-O

  4. Si=O

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Correct Option: D

Born Haber cycle is used to determine:

chemistry lattice energy born-haber cycle born-haber cycles energy cycles

  1. electron affinity

  2. lattice energy

  3. crystal energy

  4. all the above

Show answer
Correct Option: D

Choose the correct statement about the process (I) and (II).


$\displaystyle Na^{+} _{(g)}\xrightarrow{(I)}Na _{\left ( g \right )} \xrightarrow {(II)}Na _{\left ( s \right )}$

chemistry lattice energy born-haber cycle born-haber cycles energy cycles

  1. In $(I)$ energy released. $(II)$ energy absorbed

  2. In both $(I)$ and $(II)$ energy is absorbed

  3. In both $(I)$ and $(II)$ energy is released

  4. In $(I)$ energy absorbed, $(II)$ energy released

Show answer
Correct Option: C
Explanation:

The first process represents the electron affinity of $\displaystyle Na^+ $  ion which is negative.
The second process represents sublimation of $Na$. The sublimation energy is negative.
Thus, in both the processes, the energy is released.


Hence, the correct option is C.

For the maximum ionic character during bond formation ,_________ on cation and a __________ anion are required.

chemistry lattice energy born-haber cycle born-haber cycles energy cycles

  1. low charge, high charge

  2. low charge, low charge

  3. high charge , no charge

  4. none of these

Show answer
Correct Option: B
Explanation:
For an ionic interaction, both the cation and the anion should possess low charges. If the degree of polarization is quite small, ionic bonds are formed,
Otherwise, with higher degree of polarization, covalent bonds are formed
Ionic bonds result from a redox reaction in which the atoms of an element , which (usually metal) has low ionization energy, give away some of their electrons to achieve a stable electronic configuration

The standard formation reaction for aluminium oxide is $4Al(s) + 6O(g)\rightarrow 2Al _2O _3(s)$. This statement is false because:

chemistry lattice energy born-haber cycle born-haber cycles energy cycles

  1. aluminium is not in its standard state

  2. the reaction should be written for one mole of Al

  3. The reaction is prevented by a thin film of $Al _2O _3$ formed on the surface of Al

  4. none of these

Show answer
Correct Option: B
Explanation:
$2Al+3O _2\rightarrow Al _2O _3$

The enthalpy of the above reaction is enthalpy of formation as one mole of $Al _2O _3$ is forming from elemental aluminum and oxygen gas.