Tag: practical work

Questions Related to practical work

On adding $NH _4OH$ to $MnCl _2$, the precipitate formed is :

distinguish between black copper oxide and black manganese dioxide practical work chemistry

  1. $NH _4Cl$

  2. $Mn(OH) _2$

  3. no precipitate

  4. both $A$ and $B$

Show answer
Correct Option: C
Explanation:

No precipitate is formed on reaction of ammonium hydroxide with manganese chloride.

Which acid will react poorly with copper oxide?

distinguish between black copper oxide and black manganese dioxide practical work chemistry

  1. $HCl$

  2. $H _2SO _4$

  3. $H _3PO _4$

  4. $H _3PO _2$

Show answer
Correct Option: C,D
Explanation:

Acids of non metal phosphorous react poorly with copper oxide.

$CuO+2HCl\rightarrow CuCl _2+H _2O$
$CuO+H _2SO _4\rightarrow CuSO _4+H _2O$
so,$H _3PO _4,H _3PO _2$ do not react with copper oxide.

Copper oxide is a:

distinguish between black copper oxide and black manganese dioxide practical work chemistry

  1. weak acid

  2. weak base

  3. strong acid

  4. strong base

Show answer
Correct Option: B
Explanation:

Copper oxide acts as weak base because when dissolved in water it produce mild basic hydroxide$Cu(OH) _2$

The gases evolved on the reaction of manganese dioxide with $HCl$ is/are:

distinguish between black copper oxide and black manganese dioxide practical work chemistry

  1. $H _2$

  2. $Cl _2$

  3. both A and B

  4. none of these

Show answer
Correct Option: B
Explanation:

${ MnO } _{ 2 }+4HCl\rightleftharpoons { MnCl } _{ 2 }+2{ H } _{ 2 }O+{ Cl } _{ \left( g \right)  }\uparrow $

Which one is the correct option for the solubility of $CuCl _2$ in water?

distinguish between black copper oxide and black manganese dioxide practical work chemistry

  1. Sparingly soluble

  2. Completely soluble

  3. Insoluble

  4. Soluble at higher temperature

Show answer
Correct Option: B
Explanation:

$CuCl _2$ completely ionises in water hence it is completely soluble in water.

Number of moles of $HCl$ requied to test one mole of copper oxide is:

distinguish between black copper oxide and black manganese dioxide practical work chemistry

  1. $1$

  2. $2$

  3. $3$

  4. $4$

Show answer
Correct Option: B
Explanation:

$CUO+2HCl\rightarrow { CuCl } _{ 2 }+{ H } _{ 2 }O$

2 $HCl$ moles for one mole $CUO$.

Number of moles of $HCl$ requied to test one mole of manganese dioxide is:

distinguish between black copper oxide and black manganese dioxide practical work chemistry

  1. $2$

  2. $3$

  3. $4$

  4. $1$

Show answer
Correct Option: C
Explanation:

${ MnO } _{ 2 }+4HCl\rightleftharpoons { MnCl } _{ 2 }+{ Cl } _{ 2 }+2{ H } _{ 2 }O$

Clearly from equation, ${ MnO } _{ 2 }$ need $4HCl$

Number of gaseous products that manganese dioxide forms on reaction with $HCl$ is:

distinguish between black copper oxide and black manganese dioxide practical work chemistry

  1. $0$

  2. $1$

  3. $2$

  4. $3$

Show answer
Correct Option: B
Explanation:

Manganisedioxide forms one gaseous products i.e. chlorine when react with hydrochloric acid as:

$MnO _2 + 4HCl \rightarrow MnCl _2 + Cl _2 + 2H _2O$

Which of the following will produce a gas with bleaching property on reaction with hydrochloric acid?

distinguish between black copper oxide and black manganese dioxide practical work chemistry

  1. $CuO$

  2. $MnO _2$

  3. Both A and B

  4. None of these

Show answer
Correct Option: B
Explanation:

$4HCl(aq)+MnO _2(S)\longrightarrow MnCl _2+2H _2O+Cl _2$

$MnO _2$ on reaction with $HCl$ gets reduced to $MnCl _2$ and $HCl$ gets oxidised to $Cl _2$

The gases evolved on the reaction of copper oxide with $HCl$ is/are:

distinguish between black copper oxide and black manganese dioxide practical work chemistry

  1. $H _2$

  2. $Cl _2$

  3. both A and B

  4. none of these

Show answer
Correct Option: D
Explanation:

${ CUO } _{ \left( S \right)  }+{ HCl } _{ \left( aq \right)  }\rightleftharpoons { CuCl } _{ 2\left( S \right)  }+{ H } _{ 2 }O\left( l \right) $

zero gaseous products.