Tag: analytical chemistry

Questions Related to analytical chemistry

Which of the following equation is the correct one?

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

  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

Show answer
Correct Option: D
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.

Find the odd one with reasons [valency is not a criterion]: $Al(OH) _3, Pb(OH) _2, Mg(OH) _2, Zn(OH) _2$ :

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

  1. $Al(OH) _3$

  2. $Pb(OH) _2$

  3. $Mg(OH) _2$

  4. $Zn(OH) _2$

Show answer
Correct Option: C
Explanation:

$Mg(OH) _2$ is a basic hydoxide while rest are amphoteric hydroxides.

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

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

  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. $\displaystyle { \left[ { Al\left( OH \right) } _{ 7 } \right] }^{ 4- }$

Show answer
Correct Option: A
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).

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

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

  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. $\displaystyle { \left[ { Al\left( OH \right) } _{ 7 } \right] }^{ 4- }$

Show answer
Correct Option: C

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

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

  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

Show answer
Correct Option: B
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.

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.

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

  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. $H _2 SO _4, Fe (OH) _3$

Show answer
Correct Option: D
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:
$2Fe(OH) _{3} + 3H _{2}SO _{4} \rightarrow Fe _{2}(SO _{4}) _{3} +6H _{2}O$

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 ____________.

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

  1. B turns green

  2. B turns blue

  3. A turns blue

  4. A remains colourless

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Correct Option: C
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:
$Cu + Ag(NO _{3}) _{2} \rightarrow Cu(NO _{3}) _{2} + Ag$

When sodium iodide is heated with concentrate sulphuric acid,the vapour evolved is-

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

  1. Iodine

  2. ${SO} _{2}$

  3. Sulphuric acid

  4. Oxygen

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Correct Option: A
Explanation:

$2NaI+{ H } _{ 2 }{ SO } _{ 4 }\xrightarrow [  ]{ heated } { Na } _{ 2 }{ SO } _{ 4 }+2HI$
$2HI\xrightarrow [  ]{ heated }  {H} _{2}+{I} _{2}$

Which of the following equation is not correct?

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

  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

Show answer
Correct Option: C

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

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

  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

Show answer
Correct Option: A
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.