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Chemistry 1 Marks Question

Organic Chemistry: Some Basic Principles and Techniques · MP Board (MPBSE) STD 11 Science (Madhya Pradesh - English Medium). 85 questions.

Questions · Page 2 of 2

1 Marks Question

Question 511 Mark
Write the IUPAC name of:
$\ \ \ \ \ \ \ \ \ \ \ \ \ _4\ \ \ \ \ \ \ \ \ _3\ \ \ \ \ \ \ \ \ \ \ _2\ \ \ \ \ \ \ \ \ _1\\\text{CH}_3-\text{CH}-\text{CH}_2-\text{CH}-\text{COOH}\\\ \ \ \ \ \ \ \ \ \ \ \ _5|\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ |\\\ \ \ \ \ \ \ \ \ \ \ \ \text{CHO}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{CH}_3$
Answer
2, 4-Dimethyl-5-oxopentanoic acid.
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Question 521 Mark
In the organic compound $\text{CH}_2=\text{CH}-\text{CH}_2-\text{CH}_2-\text{C}\equiv\text{CH}$, the pair of hybridised orbitals involved in the formation of $\mathrm{C}_2-\mathrm{C}_3$ bond is
Answer
When double and triple bonds are present at equivalent positions, then preference is given to double bond while numbering the carbon chain. Thus
$\stackrel{{1}}{\hbox{CH}_2}=\stackrel{{2}}{\hbox{CH}}-\stackrel{{3}}{\hbox{CH}_2}-\stackrel{{4}}{\hbox{CH}_2}-\stackrel{{5}}{\hbox{C}}\equiv\stackrel{{6}}{\hbox{CH}}\\ \text{sp}^2\ \ \ \ \ \ \text{sp}^2\ \ \ \ \ \ \ \text{sp}^3\ \ \ \ \ \ \ \text{sp}^3\ \ \ \ \ \ \ \text{sp}\ \ \ \text{sp}$
$\therefore \mathrm{C}_2-\mathrm{C}_3$ bond is formed by overlap of $\mathrm{sp}^2$ and $\mathrm{sp}^3$ orbitals.
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Question 531 Mark
Give $\text{IUPAC}$ name of following bond line formula:
  1.  
  1.  
Answer
  1. $4-$methyl pentanal.
  2. $1, 2-$dimethyl cyclopentene.
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Question 541 Mark
Which of the following compounds will not exist as resonance hybrid. Give reason for your answer: $\mathrm{CH}_3 \mathrm{OH}$
Answer
$\mathrm{CH}_3 \mathrm{OH}$: it dose not show resonance because of $\pi$ electrons.
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Question 551 Mark
What is the general molecular formula of saturated monohydric alcohols?
Answer
Monohydric alcohols are the compounds derived from alkane by replacing one hydrogen by -OH group. Therefore, the general molecular formula is $\text{C}_\text{n}\text{H}_\text{2n+1}\text{OH}$
$\text{C}_\text{n}\text{H}_\text{2n+2}\text{O}$ e.g.
$\text{CH}_4\xrightarrow[\text{-H}]{ +(-\text{OH})}\text{CH}_3-\text{OH}\\ \text{Methane}\ \ \ \ \ \ \ \ \ \text{Methanol}$
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Question 561 Mark
Arrange ethyne, ethene and ethane in the order of increasing acidity.
Answer
In alkynes, due to higher electonegativity of 'sp' hybridised carbon, which is due to $50 \% \mathrm{~s}$-character, the hydrogen atom is less tightly held by the carbon and hence $\left(\mathrm{H}^{+}\right)$can be removed by a strong base. Therefore, alkynes are most acidic and alkanes are least.
$\text{CH}_3-\text{CH}_3<\text{CH}_2=\text{CH}_2<\text{HC}\equiv\text{CH}$ is increasing order of acidity.
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Question 571 Mark
Name the type of organic reaction involved in the following reaction.
$\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{I}+\mathrm{KOH}(\mathrm{aq}) \rightarrow \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{OH}+\mathrm{KI}$
Answer
This is an example of nucleophilic substitution reaction because the nucleophile $\mathrm{I}^{-}$is replaced by the nucleophile $\mathrm{OH}^{-}$.
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Question 581 Mark
Identify electrophilic centre in the following compounds $\mathrm{CH}_3 \mathrm{CH}=\mathrm{O}, \mathrm{CH}_3 \mathrm{CN}, \mathrm{CH}_3 \mathrm{I}$.
Answer
$\text{CH}_3\underline{\text{C}}\text{H}=\text{O},\ \text{H}_3\text{C}\underline{\text{C}}\equiv\equiv\text{N},$ and $\text{H}_3\underline{\text{C}}-\text{I},$ the underlined carbon atoms are electrophilic centres as they will have partial positive charge due to polarity of the C-O or C-N or C-I bonds.
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Question 601 Mark
Why is fusion of an organic compound with sodium required?
Answer
It is done so as to convert organic compound into inorganic compound which ionises in water and can be easily detected by suitable tests.
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Question 611 Mark
Which type of compounds are purified by steam distillation?
Answer
Steam volatile and insoluble in water.
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Question 621 Mark
Explain, why Lassaigne's solution is boiled with conc. $\mathrm{HNO}_3$ before testing for halogens?
Answer
It is done so as to decompose NaCN to HCN and $\mathrm{Na}_2 \mathrm{S}$ to $\mathrm{H}_2 \mathrm{S}$ which are removed as gases otherwise they will interfere with the tests for halogens.
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Question 631 Mark
What is functional group of:
  1. Aldehyde,
  2. Nitro compound?
Answer
  1. $\ \ \ \ \text{O}\\\ \ \ \ ||\\-\text{C}-\text{H}$
  1.  
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Question 641 Mark
Calculate number of sigma and pi bonds in 1,3-butadiene.
Answer
$\text{CH}_1=\text{CH}-\text{CH}=\text{CH}_2$ There are $9\sigma$ and $2\pi$ bonds present in 1,3-butadiene.
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Question 651 Mark
How will you separate a mixture of o-nitrophenol and p-nitrophenol?
Answer
Steam distillation because o-nitrophenol is steam volatile due to weaker intramolecular H-bonding while p-nitrophenol is not steam volatile due to stronger inter molecular H-bonding.
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Question 661 Mark
Write the structure of compound that contains both 1° and 2° alcohol.
Answer
$\text{CH}_2\text{OH}(1^\circ)\\ \ |\\\text{CHOH}(2^\circ)\\ \ |\\\text{CH}_2\text{OH}(1^\circ)$
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Question 671 Mark
What type of solids are separated by fractional crystallisation?
Answer
Those solids which are soluble in same solvent but to different extent, i.e. differ in their solubility. Less soluble component will crystallise out first which can be separated. On further crystallization, more soluble component will get crystallised.
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Question 701 Mark
Name two classes of compounds in which Kjeldahl's method cannot be used for estimation of nitrogen.
Answer
Nitro compounds, azo compounds and compounds containing nitrogen in ring, e.g. pyridine, quinoline.
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Question 721 Mark
Explain, why an organic liquid vapourises at a temperature below its boiling point in its steam distillation?
Answer
In steam distillation, the mixture consisting of the organic liquid and water boils when the sum of the vapour pressures of the organic liquid $\left(p_1\right)$ and that of water $\left(p_2\right)$ becomes equal to the atmospheric pressure $\left(p_1\right)$, i.e. $p=p_1+p_2$.
Since, $p_1$ is lower than $p$, the orgainc liquid vaporises at lower temperature than its boiling point.
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Question 731 Mark
Write structural formula of 3, 4, 4, 5-tetramethylheptane.
Answer
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{CH}_3\\\ \ _1\ \ \ \ \ \ \ \ \ \ _2\ \ \ \ \ \ \ \ \ \ \ _3\ \ \ \ \ \ \ _4|\ \ \ \ \ \ \ _5\ \ \ \ \ \ \ \ \ _6\ \ \ \ \ \ \ \ \ \ _7\\\text{CH}_3-\text{CH}_2-\text{CH}-\text{C}-\text{CH}-\text{CH}_2-\text{CH}_3\\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ |\ \ \ \ \ \ \ \ \ \ |\ \ \ \ \ \ \ |\\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{CH}_3\ \ \ \text{CH}_3\ \ \text{CH}_3\\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ _{3,4,4,5-\text{Tetramethylheptane}}$
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Question 741 Mark
How many o bonds and bonds are present in the second member of the alkene series?
Answer
The second member of the alkene series is propene. The structural formula of the propene is
$ \ \ \ \ \ \ \ \ {\text{H}\ \ \ \ \ \text{H}\ \ \ \ \ \text{H}}\\\ \ \ \ \ \ \ \ \ |\ \ \ \ \ \ \ |\ \ \ \ \ \ \ |\\ \text{H}-\text{C}-\text{C}=\text{C}=\text{H}\\\ \ \ \ \ \ \ \ |\\\ \ \ \ \ \ \ \text{H}$
Number of $\sigma$ bond = 8
Number of $\pi$ bond = 1
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Question 761 Mark
The $R_f$ value of A and B in a mixture determined by TLC in a solvent mixture are 0.65 and 0.42 respectively. If the mixture is separated by column chromatography using the same solvent mixture on a mobile phase, which of the two components A or B will elute first? Explain.
Answer
$R_f$ value of $A$ is 0.65 , therefore, it is less strongly adsorbed as compared to compound $B$ which has $R_f$ value of 0.42 .
Therefore, A will be eluted first.
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Question 771 Mark
Nitrogen present in nitrobenzene, azo compounds, 'N' present in ring cannot be estimated by _________.
Answer
Nitrogen present in nitrobenzene, azo compounds, 'N' present in ring cannot be estimated by Kjeldahl's method.
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Question 781 Mark
Give the IUPAC name of the following compound:
$\text{CH}_3-\text{CH}_2-\text{CH}-\text{C}-\text{H}\\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ |\ \ \ \ \ \ \ \ \ ||\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{CH}_3\ \ \ \text{O}$
Answer
$\ _4\ \ \ \ \ \ \ \ \ \ \ _3\ \ \ \ \ \ \ \ \ \ _2\ \ \ \ \ \ \ \ \ _1\\\text{CH}_3-\text{CH}_2-\text{CH}-\text{C}-\text{H}\\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ |\ \ \ \ \ \ \ \ \ ||\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{CH}_3\ \ \ \text{O}\\\ \ \ \ \ \ \ \ \ \ \ \ \ _{2-\text{Methylbutanal}}$
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Question 791 Mark
Give the IUPAC name of the following compound $\text{CH}_3-\text{CH}-\text{C}-\text{CH}-\text{CH}_3\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ | \ \ \ \ \ \ \ \ \ \| \ \ \ \ \ \ |\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{Br} \ \ \ \ \ \ \text{O} \ \ \ \ \ \text{CH}_3$
Answer
$\stackrel{{1} \ \ \ \ }{\hbox{CH}_3}-\stackrel{{2} \ \ \ }{\hbox{CH}}-\stackrel{{3} }{\hbox{C}}-\stackrel{{4} \ \ \ }{\hbox{CH}}-\stackrel{{5} \ \ \ \ }{\hbox{CH}_3}\\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ | \ \ \ \ \ \ \ \ \| \ \ \ \ \ \ |\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{Br} \ \ \ \ \ \ \text{O} \ \ \ \ \ \text{CH}_3\\ _{2-\text{bromo-4-methyl pentan-3-one}}$
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Question 811 Mark
Why is benzylic free radical more stable than allylic free radical?
Answer
This is due to more resonance of benzylic free radical.
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Question 821 Mark
Name the method used to purify aniline.
Answer
Steam distillation because it is steam volatile and immiscible with water.
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Question 831 Mark
$\text{CH}_2=\stackrel{- \ \ \ }{\text{CH}}$ is more basic than $\text{HC}\equiv\text{C}^-.$ Explain why?
Answer
$\text{CH}_2=\stackrel{\text{sp}^2}{\text{CH}^-}$ $\text{HC}\equiv\stackrel{\text{sp}}{\text{C}^-}$
Since, sp-carbon is more electronegative than $\text{sp}^2$-carbon, therefore, $\text{CH}\equiv\text{C}^-$ is less willing to donate a pair of electrons than $\text{H}_2\text{C}=\text{CH}^-.$ In other words, $\text{H}_2\text{C}=\text{CH}^-$ is more basic than $\text{HC}\equiv\text{C}^-.$
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Question 841 Mark
Identify the most electronegative element in $\mathrm{CH}_2 \mathrm{FCl}$.
Answer
'F' (fluorine) is most electronegative element.
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Question 851 Mark
How can you separate a mixture of three immiscible liquids having different boiling points?
Answer
We can separate with the help of separating funnel due to difference in densities. As they differ in boiling points, the forces of attraction between molecules will be different, therefore, they will have different densities, hence they can be separated by differential extraction using separating funnel as these are immiscible.
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