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Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Dilution of sulphuric acid is a/an:

  1. synthesis reaction

  2. exothermic reaction

  3. endothermic reaction

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Dilution of sulphuric acid with water is a highly exothermic process as it occurs with the evolution of heat. The equation for this reaction  can be wriiten as:
$H _{2}SO _{4}  +  2H _{2}O  \rightarrow   2H _{3}O^{+}  +  SO _{4}^{2-}  +  heat$

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Which of the following are endothermic process?

  1. boiling of water

  2. dissolving salts in water
  3. dissolving conc. $H _2SO _4$ in water

  4. evaporation of water
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation
  1. Boiling of water would be an endothermic process because the system (water) is absorbing heat to turn into vapour. Hence both option 1 $ 3 are endothermic.
     And the reverse process would therefore be exothermic.

    2. Addition of Conc. acids to water is an exothermic reaction.
Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Chemical reactions occur with absorption of heat energy are called:

  1. precipitation reactions

  2. exothermic reactions

  3. endothermic reactions

  4. synthesis reactions
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The term endothermic process describes a process or reaction in which the system absorbs energy from its surroundings in the form of heat where in case of exothermic it releases energy to the surroundings. 

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Which of the following is/are endothermic reactions?

  1. $CaCO _{3}\rightarrow CaO+CO _{2}$
  2. $CH _{4}+2O _{2}\rightarrow CO _{2}+2H _{2}O$
  3. $2HgO\rightarrow 2Hg+O _{2}$
  4. $2H _{2}+O _{2}\rightarrow 2H _{2}O$
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation
$CaCO _{3}\rightarrow CaO+CO _{2}$
is a decomposition reaction and requires energy for breaking bonds. Its an endothermic reaction.
$CH _{4}+2O _{2}\rightarrow CO _{2}+2H _{2}O$
Its a combustion reaction hence releases energy and is an exothermic reaction
$2HgO\rightarrow 2Hg+O _{2}$
is a decomposition reaction and requires energy for breaking bonds. Its an endothermic reaction.
$2H _{2}+O _{2}\rightarrow 2H _{2}O$
Its a combustion reaction hence releases energy and is an exothermic reaction
Thus A and D are endothermic reactions. Option A and D are correct
Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

In endothermic reactions:

  1. reactants have more energy than products

  2. reactants have less energy than products

  3. reactants and products have same energy

  4. reactants have lower temperature than products
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An endothermic occurs if the products have a higher energy level than the reactants and $\Delta H$ will be positive. In other words, reactants have lesser energy than products.

In an exothermic reaction, the reacting mixture absorbs heat from the surroundings. Therefore, the reactants will have higher energy than the product here.

So the answer is option B.

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions
For per gram reactant, the maximum quantity of ${ N } _{ 2 }$ gas is produced in which of the following thermal decomposition reaction? (Given: Atomic wt. Cr=52 u, Ba=137 u)
  1. $(NH _4) _2Cr _2O _7(s) \rightarrow N _2(g) + 4H _2O(g)+Cr _2O _3(s)$
  2. $2NH _4NO _3(s) \rightarrow 2N _2(g) + 4H _2O(g)+O _2(g)$
  3. $Ba(N _3) _2(s) \rightarrow Ba(s) + 3N _2(g)$
  4. $2NH _3(g) \rightarrow N _2(g) + 3H _2(g)$
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

Which of the following statements is wrong?

  1. Single N-N bond is stronger than the single P-P bond.
  2. $PH _{3}$ can act as a ligand in the formation of coordination compound with transition elements.
  3. $NO _{2}$ is paramagnetic in nature.
  4. Covalency of nitrogen in $N _{2}O _{5}$ is four.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

N-N sigma bond (single bod)  is weaker than P-P sigma bond (single bond) due to the small bond length between the nitrogen atoms. The lone pair of electrons of both the atoms nitrogen  repel each other making the single bon between $N-N$  weaker than P-P sigma bond.In $P-P$  bond the repulsion between sigma bond and lone pair electrons is less as the size of phosphorous is large.

So statement A is wrong.

Hence option A is correct.

Multiple choice chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

Nitrogen forms stable $N _{2}$ molecule but phosphorus is converted to $P _{4}$ from $P _{2}$ because:

  1. p$\pi$-p$\pi$ bonding is strong in phosphorus
  2. p$\pi$-p$\pi$ bonding is weak in phosphorus

  3. triple bond is present in phosphorus
  4. single $P - P$ bond is weaker than $N -N$ bond
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$P$ has empty $d$ orbital, that can be filled by an additional electron. And since its size is bigger it is least likely to handle triple bond, as size increases $\pi$ overlapping decreases. 

Multiple choice chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

Which of the following mlecular $P\pi -P\pi $ bond?

  1. ${ NO } _{ 3 }^{ - }$

  2. CO
  3. ${ CO } _{ 3 }^{ -2 }$
  4. ${ NO } _{ 4 }^{ -2 }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

CO (carbon monoxide) has a π bond between carbon and oxygen where both atoms contribute p-orbitals - a pπ-pπ bond. Nitrate and carbonate ions have resonance, and nitrate ion does not contain a double bond structure.

Multiple choice chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

Which of the following  molecules is having $2p\pi -3d\pi $ bond?

  1. ${ SO } _{ 3 }$
  2. ${ NO } _{ 3 }^{ - }$
  3. ${ SO } _{ 2- }^{ 4 }$
  4. ${ PO } _{ 3- }^{ 4 }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In sulfur trioxide (SO3), sulfur utilizes its empty d-orbitals to form pi bonds with the p-orbitals of oxygen atoms, resulting in p_pi-d_pi bonding. The other species listed either lack vacant d-orbitals of appropriate energy or do not form d-pi bonds in the same manner.