[3 Mark Question Answer]

Question 13 Marks

Using appropriate catalysts, ethane can be oxidized to an alcohol, an aldehyde and an acid. name the alcohol, aldehyde and acid formed when ethane is oxidized.

Answer

Ethane $\rightarrow$ Alcohol
$
2 C _2 H _6+ O _2 \xrightarrow[200^{\circ} C ]{ Cu } 2 C _2 H _5 OH
$
The alcohol is ethanol.
Ethane $\rightarrow$ Aldehyde
$
C _2 H _6+ O _2 \xrightarrow{350^{\circ} C } MoO _3 CHO + H _2 O
$
The Aldehyde formed is ethanol.
Ethane $\rightarrow$ Acid
$
C _2 H _6+ O _2 \xrightarrow[350^{\circ} C ]{ MoO } CH _3 CHO + H _2 O
$
$
Ch _3 CHo +[ O ] \xrightarrow[\text { conc } \cdot H _2 SO _4]{ K _2 Cr _2 O _7} CH _3 COOH
$

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Question 23 Marks

Distinguish between the saturated hydrocarbon ethane and the unsaturated hydrocarbon ethene by drawing their structural formulae.

Answer

Ethane	Ethene
$\begin{array}{cc} \phantom{........}\ce{H}\phantom{...}\ce{H}\phantom{........}\\ \phantom{....}\|\phantom{...} \phantom{.}\|\phantom{....}\\ \ce{H-C-C-H}\\ \phantom{....}\|\phantom{...} \phantom{.}\|\phantom{....}\\ \phantom{........}\ce{H}\phantom{...}\ce{H}\phantom{........}\\ \end{array}$	$\begin{array}{cc} \phantom{........}\ce{H}\phantom{...}\ce{H}\phantom{........}\\ \phantom{....}\|\phantom{...} \phantom{.}\|\phantom{....}\\ \ce{C = C}\\ \phantom{....}\|\phantom{...} \phantom{.}\|\phantom{....}\\ \phantom{........}\ce{H}\phantom{...}\ce{H}\phantom{........}\\ \end{array}$
It has carbon - carbon single bond.	It has carbon - carbon double bond
It is saturated.	It is unsaturated
Alkanes undergo a substitution reaction.	Alkenes undergo addition reaction.

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Question 33 Marks

Copy and complete the following table which relates to three homologus series of hydrocarbons:

General formula	$C_nH_{2n}$	$C_nH_{2n-2}$	$C_nH_{2n+2}$
IUPAC name of the homologus series
Characteristic bond type			Single bond
IUPAC name of the first member of the series
Type of reaction with chlorine		Addition

Answer

The homologous series of hydrocarbons are :

General formula	$C_nH_{2n}$	$C_nH_{2n-2}$	$C_nH_{2n+2}$
IUPAC name of the homologus series	Alkenes	Alkynes	Alkanes
Characteristic bond type	Double bond	Triple bond	Single bond
IUPAC name of the first member of the series	Ethene	Ethyne	Methane
Type of reaction with chlorine	Addition	Addition	Substitution

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Question 43 Marks

For each of the compounds : (a) ethane (b) vinegar (c) Marsh gas draw the relevant structural formula

Answer

Structural formula are as under:
(a) Ethane
$\begin{array}{cc}
\phantom{........}\ce{H}\phantom{...}\ce{H}\phantom{........}\\
\phantom{....}|\phantom{...} \phantom{.}|\phantom{....}\\
\ce{H-C-C-H}\\
\phantom{....}|\phantom{...}\phantom{.}|\phantom{....}\\
\phantom{........}\ce{H}\phantom{...}\ce{H}\phantom{........}\\
\end{array}$
(b) Vinegar
$\begin{array}{cc}
\phantom{...............}\ce{H}\phantom{.....}\ce{O}\phantom{.........}\\
\phantom{.........}|\phantom{...} \phantom{.}//\phantom{....}\\
\ce{H-C-C}\\
\phantom{.......}|\phantom{...}\phantom{.}\text{\\} \phantom{..}\\
\phantom{...................}\ce{H}\phantom{}\phantom{....}\ce{O-H}\phantom{.........}\\
\end{array}$
(c) Marsh gas
$\begin{array}{cc}
\ce{H}\\
|\\
\ce{H-C-H}\\
|\\
\ce{H}
\end{array}$

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Question 53 Marks

Write the important uses of acetic acid.

Answer

Uses of acetic acid:

As a solvent for gums, resin, cellulose atc
As a laboratory reagent
In medicines
As a vinegar for table purpose and for manufacturing pickles
For making rubber, rayon, plastic, varnishes atc.
For the manufacture of dyes, perfumes, pigments.

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Question 63 Marks

Write the molecular formulae and structure formula of ethanic acid?

Answer

Sructure formula of ethanoic acid:
$\begin{array}{cc}
\phantom{.....}\ce{H}\phantom{...}\ce{O}\phantom{........}\\
\phantom{.}|\phantom{...} \phantom{.}||\phantom{....}\\
\ce{H-C-C-O-H}\\
\phantom{}|\phantom{...}\phantom{.}\phantom{....}\\
\phantom{....}\ce{H}\phantom{...}\ce{}\phantom{........}\\
\end{array}$
Molecular formula of Ethanoic acid:
$CH_3COOH$

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Chemistry [3 Mark Question Answer]

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