Tag: chemistry

Questions Related to chemistry

The type of bonding present in a substance can be determined from experimental data.
Based on the information in the table below, which of the following substances is most likely to represent the identity of the solid?

Melting Point Density Conductivity Alone Conductivity in Aqueous Solution
$801^{\circ}C$ $2.17\ g/cc$ None Excellent
chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. Platinum, $Pt$

  2. Sodium chloride, $NaCl$

  3. Glucose, $C _{6}H _{12}O _{6}$

  4. Quartz, $SiO _{2}$

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Correct Option: B

Which of the following materials conducts electricity?

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. Crystalline potassium chloride

  2. Fused sulphur

  3. Molten sodium chloride

  4. Diamond

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Correct Option: C
Explanation:

In crystalline solids, the ions are tightly bound by strong coulombic force of attraction having greater interatomic interaction and less interparticle space. $ { Na }^{ + }$ and ${ Cl }^{ - } $ ions are free to move only in molten state or aqueous solution. Hence, they show electrical conductivity in molten state.

Brine is:

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. aqueous solution of chloride

  2. saturated solution of $NaCl$

  3. aqueous solution of $HCl$

  4. common name of bleaching powder

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Correct Option: B
Explanation:

Brine is a solution of salt ( usually sodium chloride ) in water.

Molten $NaCl$ conducts electricity due to the presence of:

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. Free molecules

  2. Free ions

  3. Free electrons

  4. Free atoms

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Correct Option: B
Explanation:

Molten sodium chloride contains sodium ions and chloride ions which are free to move. 


Hence molten sodium chloride conducts electricity.

Option B is correct.

Crude common salt is hygroscopic because of impurities of:

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. $CaSO _{4}$ and $MgSO _{4}$

  2. $CaCl _{2}$ and $MgCl _{2}$

  3. $CaBr _{2}$ and $MgBr _{2}$

  4. $Ca\left ( HCO _{3} \right ) _{2}$ and $Mg\left ( HCO _{3} \right ) _{2}$

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Correct Option: B
Explanation:

Crude common salt contains impurities such as $ CaSO _{ 4 },   CaCl _{ 2 } ,   MgCl _{ 2} $. Hence it is deliquescent (hygroscopic).

Hence option B is correct.

Molten sodium chloride conducts electric current due to the presence of:

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. free electrons

  2. free mobile ions

  3. immobile ions

  4. none of these

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Correct Option: B
Explanation:

Current is the rate of flow of charge. NaCl is an ionic solid. An ionic solid consists of a lattice of ${ Na }^{ + }$ and ${ Cl }^{ - }$ ions in which these ions are fixed in their places. Solid NaCl does not contain any mobile charge carriers that can facilitate the flow of charge. But molten NaCl contains free mobile ions ${ Na }^{ + }$ and ${ Cl }^{ - }$ ions which allow the passage of current.


Thus, molten NaCl conducts electric current due to the presence of free mobile ions.

When a chemical reaction takes place, during the course of the reaction the rate of reaction?

chemistry reaction kinetics determining rates graphically calculating rate of reaction graphically rate of a chemical reaction

  1. Keeps on increasing with time

  2. Remains constant with time

  3. Keeps on decreasing with time

  4. Shows irregular trend with time

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Correct Option: C
Explanation:

Rate of reaction $\propto$ conc. of reactants
As the reaction proceeds, concentration of the reactants decreases hence the rate also keeps on decreasing with time.

In a reaction $2HI \rightarrow H _{2} + I _{2}$, the concentration of $HI$ decreases from $0.5\ mol\ L^{-1}$ to $0.4\ mol\ L^{-1}$ in $10$ minutes. What is the rate of reaction during this interval?

chemistry reaction kinetics determining rates graphically calculating rate of reaction graphically rate of a chemical reaction

  1. $5\times 10^{-3} M\ min^{-1}$

  2. $2.5\times 10^{-3} M\ min^{-1}$

  3. $5\times 10^{-2} M\ min^{-1}$

  4. $2.5\times 10^{-2} M\ min^{-1}$

Show answer
Correct Option: A
Explanation:

Average rate $= -\dfrac {1}{2} \dfrac {\triangle [R]}{\triangle t} = -\dfrac {1}{2}\times \dfrac {0.4 - 0.5}{10}$


$= \dfrac {1}{2}\times \dfrac {0.1}{10} = 5\times 10^{-3}M\ min^{-1}$.

Which of the following statements is correct?

chemistry reaction kinetics determining rates graphically calculating rate of reaction graphically rate of a chemical reaction

  1. The rate of a reaction decreases with passage of time as the concentration of reactants decreases.

  2. The rate of a reaction is same at any time during the reaction.

  3. The rate of a reaction is independent of temperature change.

  4. The rate of a reaction decreases with increase in concentration of reaction(s).

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Correct Option: A
Explanation:

According to rate law expression,
$Rate \propto [R]$
Thus, rate of a reaction decreases with passage of time as the concentration of reactants decreases.

The rate constant of a zero order reaction is 0.2 mol $d{ m }^{ -3 }{ h }^{ -3 }$. If the concentration minutes is 0.05 mol $d{ m }^{ -3 }$. Then its initial concentration would be:

chemistry reaction kinetics determining rates graphically calculating rate of reaction graphically rate of a chemical reaction

  1. $6.05 mol d{ m }^{ -3 }$

  2. $0.15 mol d{ m }^{ -3 }$

  3. $0.25 mol d{ m }^{ -3 }$

  4. none of the above

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Correct Option: B