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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

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.

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

Multiple choice chemistry study of the first element - hydrogen occurrence of hydrogen introduction to hydrogen hydrogen

Metals like .......... , ........... and .......... give $H _2$ with steam.

  1. iron

  2. magnesium

  3. aluminium

  4. sodium

  5. calcium

  6. none of the above
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

Metals which react with steam to give $H _2$ gas are Iron, Magnesium and Aluminium.


Magnesium ribbon reacts with steam to give Magnesium oxide and Hydrogen gas.

$Mg$ $+$ $H _2O$ $=$ $MgO$ $+$ $H _2$

Aluminium reacts with steam to give Aluminium Oxide and Hydrogen gas. But the reaction takes place very slowly, as a layer of Aluminium Oxide forms on the metal.

$2Al$ $+$ $3H _2O$ $=$ $Al _2O _3$ $+$ $3H _2$
Iron does not react with cold water. It reacts with steam to form Ferric Oxide and hydrogen gas.

$3Fe$ $+$ $4H _2O$ $=$ $Fe _3O _4$ $+$ $4H _2$
Thus, options A, B  and C are correct.

Multiple choice chemistry study of the first element - hydrogen occurrence of hydrogen introduction to hydrogen hydrogen

At $298 \, K$ , assuming ideal behaviour, the average kinetic energy of a deuterium molecule is :

  1. Two times that of a hydrogen molecule

  2. Four times that of a hydrogen molecule

  3. Half of that of a hydrogen molecule

  4. Same as that of a hydrogen molecule
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Average Kinetic Energy depends only on temperature

$\displaystyle (KE) _{avg} = \frac {3kT} {2} $ per molecule

Multiple choice chemistry study of the first element - hydrogen occurrence of hydrogen introduction to hydrogen hydrogen

Under suitable conditions, the following reaction:
Metal+Water $\xrightarrow [  ]{ Heat } $ Oxide or hydroxide of metal + Hydrogen 

may take place? Find which of the following metals, does not react in this way.

  1. Sodium

  2. Copper

  3. Iron

  4. Magnesium
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Because $Cu$ is placed below ${ H } _{ 2 }$ in reactivity series, hence cannot displace ${ H } _{ 2 }$. Hence reaction does not occur.