Tag: action of alkalis on some metals and metal oxides

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Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

Which of the following equation is the correct one?

  1. Amphoteric oxide / Hydroxide + acid$\rightarrow$ Salt + Hydrogen
  2. Amphoteric oxide / Hydroxide + alkali$\rightarrow$ Salt + Hydrogen
  3. Metal + alkali$\rightarrow$ Salt + Water
  4. Metal + alkali$\rightarrow$ Salt + Hydrogen
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Amphoteric oxide reacts with acid/alkali to produce salt and water not salt and hydrogen. Also, Metal and alkali react to give salt and liberate hydrogen not water. So, option D is correct.

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

When aluminium hydroxide is reacted with excess sodium hydroxide, the soluble amphoteric compound is formed. Mark the correct formula. 

  1. $\displaystyle { \left[ { Al\left( OH \right) } _{ 4 } \right] }^{ - }$
  2. $\displaystyle { \left[ { Al\left( OH \right) } _{ 5 } \right] }^{ 2- }$
  3. $\displaystyle { \left[ { Al\left( OH \right) } _{ 6 } \right] }^{ 3- }$
  4. $\displaystyle { \left[ { Al\left( OH \right) } _{ 7 } \right] }^{ 4- }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$Al(OH) _3 + NaOH \rightarrow Na^+ [Al(OH) _4]^-$

 Aluminium hydroxide when reacted with excess sodium hydroxide, the soluble amphoteric compound  formed is sodium tetra hydroxoaluminate (III).

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

When aluminium hydroxide is reacted with excess ammonium hydroxide, the insoluble compound is formed. Mark the correct formula.

  1. $\displaystyle { \left[ { Al\left( OH \right) } _{ 4 } \right] }^{ 1- }$
  2. $\displaystyle { \left[ { Al\left( OH \right) } _{ 5 } \right] }^{ 2- }$
  3. $\displaystyle { \left[ { Al\left( OH \right) } _{ 6 } \right] }^{ 3- }$
  4. $\displaystyle { \left[ { Al\left( OH \right) } _{ 7 } \right] }^{ 4- }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Aluminium hydroxide reacts with excess hydroxide ions to form the soluble tetrahydroxoaluminate complex, [Al(OH)4]-. However, in some contexts, the hexahydroxoaluminate complex [Al(OH)6]3- is also discussed in coordination chemistry.

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

If the pH of an alkali metal hydroxide is 13.6, the concentration of hydroxide is ;

  1. More than 1 M

  2. Between 0.1 M and 1 M

  3. Between 0.01 M and 1 M

  4. Less than 0.001 M
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Given that :

$pH = 13.6$

Thus, $pOH = 14 - 13.6$

                     $=0.4$
Hence,
$[O{H^ - }] = lo{g^{ - 1}}( - 0.4)$

               $ = 0.3979$

Therefore the value of $[O{H^ - }]$ is between $0.1M$ and $1M$.

Therefore, the option is B.

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

A salt contains two atoms of iron, three atoms of sulphur and twelve atoms of oxygen. Identify the corresponding acid and base from which it is formed.

  1. $H _2 SO _4, Fe (OH) _2$
  2. $H _2 SO _3, Fe (OH) _2$
  3. $H _2 SO _3, Fe (OH) _3$
  4. $H _2 SO _4, Fe (OH) _3$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$Fe _{2}(SO _{4}) _{3}$ is the salt formed from $Fe(OH) _{3}$ and $H _{2}SO _{4}$. The balanced chemical equation can be written as:
$2Fe(OH) _{3} + 3H _{2}SO _{4} \rightarrow Fe _{2}(SO _{4}) _{3} +6H _{2}O$

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

Colourless solution of silver nitrate is taken in two test tubes A and B. Metal plates of copper and platinum are dipped into test tubes, A and B respectively. Content of test tubes ____________.

  1. B turns green

  2. B turns blue

  3. A turns blue

  4. A remains colourless
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In test tube A, displacement reaction takes place as copper being more reactive displaces silver from silver nitrate solution thus leading to the formation of copper nitrate which is blue in colour. The chemical reaction can be written as:
$Cu + Ag(NO _{3}) _{2} \rightarrow Cu(NO _{3}) _{2} + Ag$

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

Which of the following equation is not correct?

  1. Amphoteric oxide / Hydroxide + Acid$\rightarrow$ Salt + Water
  2. Amphoteric oxide / Hydroxide + Alkali$\rightarrow$ Salt + Water
  3. Metal + Alkali$\rightarrow$ Salt + Water
  4. Metal + Alkali$\rightarrow$ Salt + Hydrogen
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Metals generally do not react with alkalis to produce water; they react with alkalis to produce hydrogen gas and a salt (for amphoteric metals like Al or Zn). Therefore, 'Metal + Alkali -> Salt + Water' is incorrect.

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

Which of the following equation represents action of alkali on oxide?

  1. $ZnO+2NaOH\rightarrow Na _2ZnO _2+H _2O$
  2. $Zn\begin{pmatrix}OH\end{pmatrix} _2+2NaOH\rightarrow NaZnO _2+2H _2O$
  3. $PbO+2NaOH\rightarrow Na _2PbO _2+2H _2O$

  4. Both A and C
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Oxides of certain metals react with acid and alkali to give salt and water.
$ZnO+2NaOH\rightarrow Na _2ZnO _2+H _2O$ is the only correct equation.