Tag: distinguish between black copper oxide and black manganese dioxide

Questions Related to distinguish between black copper oxide and black manganese dioxide

$CuO$ reacts with $HCl$ but $Cu$ does not, why?

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

  1. Copper has a higher reduction potential than hydrogen, it does not react with non-oxidising acids like $HCl$

  2. Copper has a lower reduction potential than hydrogen, it does not react with non-oxidising acids like $HCl$

  3. Copper is a least reactive metal hence does not react with any acid

  4. Both $Cu$ and $CuO$ does not react with $HCl$

Show answer
Correct Option: A
Explanation:

Copper does not react with $HCl$ acid, but copper oxide does react. Copper has a higher reduction potential than hydrogen, hence it does not react with non-oxidising acids like $HCl$ or dil.$H _2SO _4$.
But metal oxides are basic substances, and so they generally react with acids forming respective salt and water. 

On reacting copper oxide with hydrochloric acid and filtering it, the filtrate is of which colour?

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

  1. Blue

  2. Yellow

  3. Black

  4. Brown

Show answer
Correct Option: A
Explanation:

On reacting copper oxide with $HCl$ and filtering it, copper chloride is formed which is blue in colour.

On adding hydrochloric acid to $MnO _2$, which gas is evolved?

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

  1. $H _2$

  2. $Cl _2$

  3. $O _2$

  4. None of the above

Show answer
Correct Option: B
Explanation:

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

Greenish yellow gas chorine is evolved.

Why should the reaction between manganese dioxide and hydrochloric acid carried out in a fume cupboard?

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

  1. Manganese causes skin irritations

  2. Both reactants and products causes itching

  3. Chlorine gas is poisonous

  4. None of above

Show answer
Correct Option: C
Explanation:

When manganese dioxide is treated with hydrochloric acid, chlorine gas is released as a product which can be poisonous. Hence, the procedure should take place in a fume cupboard to prevent any harmful effects.

The blue colour filtrate formed after reaction of $HCl$ with $CuO$ is :

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

  1. $CuCl _2$

  2. $CuCl$

  3. $CuCl _3$

  4. $CuCl _4$

Show answer
Correct Option: A
Explanation:

The blue coloured filtrate formed after the reaction of $HCl$ with $CuO$ is $CuCl _2$.

When manganese dioxide is treated with HCl, the oxidising agent in the reaction is__________.

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

  1. $MnO _2$

  2. $HCl$

  3. $H _2O$

  4. The reaction is not a redox reaction

Show answer
Correct Option: A
Explanation:

When Manganese dioxide reacts with $HCl$, it gives chlorine gas, water and $MnCl _2$. $MnO _2$ is the oxidising agent as it oxidises $HCl$ to $Cl _2$ which loses the hydrogen atom.

On reacting $MnO _2$ with $HCl$,
1. $Mn^{4+}$ is reduced to      
2. $Cl^{-}$ is oxidised to

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

  1. $Mn^{3+}, Cl^{4+}$

  2. $Mn^{2+}, Cl$

  3. $Mn, Cl$

  4. $Mn$ is not reduced nor $Cl$ is oxidised

Show answer
Correct Option: B
Explanation:

Manganese dioxide on reacting with hydrochloric acid, undergoes redox reaction. $MnO _2$ is the oxidising agent while $HCl$ is the reducing agent. $Mn^{4+}$ is thus reduced to $Mn^{2+}$ whereas, $Cl^{-}$ is oxidised to $Cl$.

On adding $HCl$ to copper oxide the color of the product is__________.

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

  1. pink

  2. black

  3. green

  4. white

Show answer
Correct Option: C
Explanation:

When copper oxide is treated with $HCl$, the products formed $CuCl _2$ and water. The colour of the product formed is bluish green.

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.