Tag: ionic equilibrium

Questions Related to ionic equilibrium

Two elements have electronegativity of 1.2 and 3.0. Bond formed between them would be ________________.

  1. predominantely ionic

  2. predominantely covalent

  3. co-ordinate bond

  4. metallic bond


Correct Option: A
Explanation:

Difference of electronegativity between the two atoms is 1.8 so the bond would be predominantly ionic and less covalent. For a bond to be 50% ionic and 50% covalent, the difference between electronegativities should be equal to 1.7.

Which of the following statements are correct about dissociation?

  1. Dissociation generally refers to breaking a compound into smaller pieces, usually reversibly.

  2. Dissociation can happen without the formation of charged species

  3. Both $A$ and $B$

  4. None of these


Correct Option: C
Explanation:

Dissociation in chemistry and biochemistry is a general process in which molecules (or ionic compounds such as salts, or complexes) separate or split into smaller particles such as atoms, ions or radicals, usually in a reversible manner. It may or may not form charged species as shown below. 

i). $NaCl \leftrightharpoons Na^++Cl^-$

ii). $N _2O _4 \leftrightharpoons 2NO _2$

Which of the following compounds will be dissociated into its constituent ions?

  1. Solid $NaCl$

  2. Molten $NaCl$

  3. Solid $CaCl _2$

  4. Molten $CaCl _2$


Correct Option: B,D
Explanation:

When electric current is passed through an electrolyte in its molten or aqueous state, the electrolyte is dissociated into its constituent ions.
Molten $NaCl$ breaks down to form $Na^+$ and $Cl^-$ where Sodium transfers its valence electron to Chlorine. So Sodium gets one positive charge and Chlorine gets one negative charge.
Molten $CaCl _2$ breaks down to form $Ca^{2+}$ and two $Cl^-$ ion where Calcium transfers its two valence electron to Chlorine. Hence Calcium gets two positive charges and each Chlorine atom gets one negative charge.

Acid strength and acid concentration represents:

  1. degree of dissociation and amount dissolved respectively

  2. amount dissolved and degree of dissociation respectively

  3. degree of dissociation and valency respectively

  4. none of the above


Correct Option: A
Explanation:

 Acid Strength refers to the degree of dissociation ( or ionization) in an aqueous solution. The greater the number of ions dissociated, or the number of cations and anions released in solution, the stronger the acid. Thus,  hydrochloric acid  dissociates completely into $H^+$ and $Cl^-$ ions in solution, so it is very strong. Acetic acid $(CH _3COOH)$,  dissociates feebly and releases few ions in solution, so it is  a weak acid.
Acid Concentration represents the amount of acid dissolved in a solvent. It is  measured in molarity ( the number of moles of acid in 1 L of acid solution), parts per million or percentage. The concentration is a ratio of the solute to solvent content of a solution. Acidic solutions with low numbers of acidic molecules/ions in solution are called dilute solutions whereas those with high numbers of acidic molecules/ions are called concentrated solutions.

Dissociation of molecules can be heterolytic or homolytic but ionisation is always heterolytic.

  1. True

  2. False


Correct Option: A
Explanation:

Dissociation generally refers to breaking a compound into smaller pieces, usually reversibly. You can have dissociation without the formation of charged species.

For the dissociation of a covalent bond the electron is initially shared between both atoms, thus the dissociation event into ions involves the transfer of an electron from one atom to the other, and hence is also termed ionization.

Which of the following compounds will be dissociated into its constituent ions?

  1. Aqueous $KCl$

  2. Solid $KCl$

  3. Aqueous $MgCl _2$

  4. Solid $MgCl _2$


Correct Option: A,C
Explanation:

When electric current is passed through an electrolyte in its molten or aqueous state, the electrolyte breaks up into its constituent ions.
When aqueous $KCl$ undergoes electrolysis, the ions $K^+$ and $Cl^-$ are formed where potassium transfers its one valence electron to Chlorine. So potassium becomes positively charged and chlorine becomes negatively charged.
When aqueous $MgCl _2$ undergoes electrolysis, the ions $Mg^{2+}$ and two $Cl^-$ ions are formed where magnesium transfers its two valence electron to chlorine. Thus magnesium gets two positive charges and each chlorine gets one negative charge.

The degree of ionisation does not depend upon :

  1. its nature

  2. its volume

  3. its dilution

  4. its temperature


Correct Option: B
Explanation:

The degree of ionization depends on nature of electrolyte, dilution of electrolyte, and temperature but does not depend on the volume of electrolyte.


$NaCl \longrightarrow Na^+ +Cl^-$
The above reaction is ionization or dissociation?

  1. Dissociation

  2. Ionization

  3. Both ionization and dissociation

  4. None of these


Correct Option: A
Explanation:

Dissociation is a general process in which molecules (or ionic compounds such as salts, or complexes) separate or split into smaller particles such as atoms, ions or radicals, usually in a reversible manner.

Hence, $ NaCl(aq.)\quad \rightleftarrows \quad { Na }^{ + }(aq.)\quad +\quad { Cl }^{ - }(aq.) $  is a dissociation reaction.

What is a net ionic equation?

  1. An equation that includes only the substances that are actually participating in the reaction.

  2. An equation that includes all the substances that are in the reaction.

  3. A equation written so that all ions are shown.

  4. An equation written so all charges are balanced on each side.

  5. An equation that includes only ions.


Correct Option: A
Explanation:

A net ionic equation is an equation that includes only the substances that are actually participating in the reaction.

Which of the followings is/are dissociation and not ionization?

  1. $H _2O \rightarrow H^+ + OH^-$

  2. $HCl \rightarrow H^+ + Cl^-$

  3. $Cl _2 \rightarrow 2Cl^.$

  4. $KCl \rightarrow K^+ + Cl^-$


Correct Option: C,D
Explanation:

Dissociation is a general process in which molecules (or ionic compounds such as salts, or complexes) separate or split into smaller particles such as atoms, ions or radicals, usually in a reversible manner.

$ { Cl } _{ 2 }\rightarrow 2{ Cl }^{ \bullet  } $ - Radical formation is there.

$ KCl\rightarrow { K }^{ + }+{ Cl }^{ - } $ - Ion formation is there.