Tag: properties of acids and bases

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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

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.

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 hydroxide?

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

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

$Zn\begin{pmatrix}OH\end{pmatrix} _2+2NaOH\rightarrow Na _2ZnO _2+2H _2O$ represents action of alkali on hydroxide.

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 aluminium hydroxide?

  1. $Al\begin{pmatrix}OH\end{pmatrix} _3+NaOH\rightarrow NaAlO _2+2H _2O$
  2. $Al\begin{pmatrix}OH\end{pmatrix} _3+2KOH\rightarrow2KAlO _2+H _2O$
  3. $Al\begin{pmatrix}OH\end{pmatrix} _3+KOH\rightarrow KAlO _2+2H _2O$

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

Aluminium hydroxide reacts with sodium hydroxide or potassium hydroxide to form the corresponding aluminate. Both Al(OH)3 + NaOH -> NaAlO2 + 2H2O and Al(OH)3 + KOH -> KAlO2 + 2H2O are valid representations of this reaction.

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

Complete the following equation
$Pb\begin{pmatrix}OH\end{pmatrix} _2+NaOH\rightarrow$

  1. $Pb\begin{pmatrix}OH\end{pmatrix} _2+2NaOH\rightarrow Na _2PbO _2+2H _2O$
  2. $Pb\begin{pmatrix}OH\end{pmatrix} _2+NaOH\rightarrow2Na _2PbO _2+H _2O$
  3. $Pb\begin{pmatrix}OH\end{pmatrix} _2+2NaOH\rightarrow Na _2PbO _2+H _2O$
  4. $Pb\begin{pmatrix}OH\end{pmatrix} _2+NaOH\rightarrow Na _2PbO _2+2H _2O$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$Pb\begin{pmatrix}OH\end{pmatrix} _2+2NaOH\rightarrow Na _2PbO _2+2H _2O$

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

Chromium hydroxide on reaction with excess $\displaystyle NaOH$ gives a soluble compound. Guess the molecular formula.

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

An excess of sodium hydroxide solution is added to a solution of the hexaaquachromium(III) ions to produce a solution of green hexahydroxochromate(III) ions.

$[Cr(H _2O) _6]^{3+} \xrightarrow{NaOH} [Cr(H _2O) _3(OH) _3] \xrightarrow{excess NaOH} [Cr(OH) _6]^{-3}$