Tag: chemistry

Quizzes (490) Questions (9892)

Questions Related to chemistry

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

Standard enthalpy of formation $(\Delta H _f)$ of which of the following is zero at $25^0C$ ?

  1. White phosphorous

  2. Red phosphorous
  3. Red lead $(Pb _3O _4)$
  4. $H^+(g)$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

White phosphors is the elemental form of phosphorus for which enthalpy of formation is zero, while, $H^+$ and $Pb _3O _4$ are not elemental forms.

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

The enthalpy of hydrogenation for $1-pentene$ is $+126\ kJ/mol$. The enthalpy of hydrogenation for $1, 3-pentadiene$ is $+230\ kJ/mol$. Hence estimate the resonance magnitude of (delocalization) energy of $1, 3-pentadiene$.

  1. $22\, kJ/mol$
  2. $104\, kJ/mol$
  3. $252\, kJ/mol$

  4. cannot be calculated from this information
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Enthalpy of hydrogenation per bond$=+126\ kJ/mol$


Enthalpy of hydrogenation for 2 bonds$=+252\ kJ/mol$


Resonance energy$=252-230=22\ kJ/mol$

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

The heats of neutralization of $CH _3COOH.HCOOH, HCN$ and $HClO$ are 13.2, 13.4,2.9 and 3.6 kcal/eq respectively. Then, the degree of hydrolysis for the respective ions will be in the order :

  1. $CH _3COO^- < HCOO^- < CN^- < ClO^-$
  2. $HCOO^- < ClO^- < CN^- < CH _3COO^-$
  3. $CH _3COO^- < CN^- < ClO^- < HCOO^-$
  4. $HCOO^- < CH _3COO^- < ClO^- < CN^-$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Strong acid have high heat of neutralization and are very much stable so required high energy for dissociation. Hence, weak acids are hydrolysed at faster rate than strong acids.

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

The heat change for the reaction: $C(s) + S(s)\rightarrow CS _2(l)$, known as:

  1. heat of transition

  2. heat of fusion

  3. heat of vapourisation

  4. heat of formation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
$C(s)+2S(s)\rightarrow CS _2(l)$
The heat change of the reaction is enthalpy of formation as 1 mole of $CS _2$ is being formed from elemental state of carbon as well as Sulphur.
Multiple choice chemistry chemical bond and chemical equation properties of covalent compounds types of bonds and properties covalent bond

Which statement about bonding is not correct?

  1. Carbon can form four single covalent bonds

  2. Chlorine atoms react to gain a noble gas electronic structure

  3. Covalent bonding involves losing and gaining electrons
  4. Hydrogen molecules have the formula $H _{2}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation


Solution:- (C) Covalent bonding involves losing and gaining electrons

Covalent bonding involves sharing of electrons while the losing and gaining of electrons is found in ionic bonding.

Multiple choice chemistry chemical bond and chemical equation properties of covalent compounds types of bonds and properties covalent bond

Covalent bonds are formed when electrons are $1$ .
Most covalent compounds have $2$ electrical conductivity.
Which words correctly complete gaps $1$ and $2$?

  1. Shared - high

  2. Shared - low

  3. Transferred - high

  4. Transferred - low
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Solution:- (B) Shared - low

  1. Covalent bonds are formed by sharing of electrons.
  2. Most covalent compounds have low electrical conductivity due to low mobility, i.e., no free electrons.

Multiple choice chemistry chemical bond and chemical equation properties of covalent compounds types of bonds and properties covalent bond

Compound $X$ consists of molecules.
In the liquid state X will

  1. becomes ionic

  2. be an electrolyte but not conduct electricity.

  3. conduct electricity only

  4. not conduct electricity

  5. non of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Compound X consists of molecules, so its covalent compounds and dont have any charged ions to conduct electricity so it will not conduct electricity.