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Science · 2023 · 5 marks
CBSE 2023 · Region 5 · Set 2 · Q36
(a) (i) Butane had both Carbon - Carbon bonds as well as Carbon - Hydrogen bonds. Draw its structural formula and state the number of (1) C - H bonds…
(i)
Butane had both Carbon - Carbon bonds as well as Carbon - Hydrogen bonds. Draw its structural formula and state the number of ($\displaystyle 1$) $\displaystyle \mathrm{C}-\mathrm{H}$ bonds and ($\displaystyle 2$) $\displaystyle \mathrm{C}-\mathrm{C}$ bonds in it.
(ii)
You have two carbon compounds with the molecular formula $\displaystyle \mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}$. Name two compounds with this formula and also draw their structural formula.
(i)
What is saponification ? Differentiate between soaps and detergents on the basis of the following :
(1)
Their chemical composition
(2)
Their mechanism in hard water
(ii)
Explain the formation of micelles between oily dirt and soap molecules. Also draw its diagram. The following questions are source-based/case-based questions. Read the case carefully and answer the questions that follow.
Marking-scheme solution
(i)
Number of $\displaystyle \mathrm{C}-\mathrm{H}$ bonds $\displaystyle =10$
Number of $\displaystyle \mathrm{C}-\mathrm{C}$ bonds $\displaystyle =3$
(ii)
• Propanone
Propanal
(i)
It is a reaction in which an alkali reacts with an ester to form
alcohol and a salt of carboxylic acid. /
Alternate Answer of b (i)
\[\mathrm{CH}_{3} \mathrm{COOC}_{2} \mathrm{H}_{5}+\mathrm{NaOH} \longrightarrow \mathrm{CH}_{3} \mathrm{COONa}+\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}
\]
| Soap | Detergent | |
| ($\displaystyle 1$) | Sodium or potassium salts of long chain carboxylic acids . $\displaystyle \left(\mathrm{RCOO}^{-} \mathrm{Na}^{+}\right)$ | Sodium salts of long chain Sulphonic acid ( $\displaystyle \mathrm{ROSO}_{3} \mathrm{Na}^{+}$) |
| / ammonium salts of chloride or bromide ions. | ||
| ($\displaystyle 2$) | Forms an insoluble scum in hardwater . | Does not form insoluble scum in hard-water. |
(ii)
Micelle formation :
The ionic end of soap dissolves in water while the carbon chain dissolves in
oily dirt. The soap molecules, thus form structures called micelles where
one end of the molecules is towards the oil droplet while the ionic side
faces outside.
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CBSE Class 10 Science past-paper question from the 2023 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.