JEE 2018 :: Chemistry (2018) :: Solved questions (2018)

• Chemistry (2018) - Solved questions (2018)

Glucose on prolonged heating with HI gives

Answer:

Explanation:

HI is a strong reducing agent.It reduces both primary and secondary alcoholic groups of glucose along with the carbonyl group to produce n-hexane as

The recommended concentration of fluoride ion in drinking water is up to 1 ppm as fluroide ion is required to make teeth enamel harder by converting [3Ca₃(PO₄)₂.Ca (OH)₂]  to

Answer:

Explanation:

Fluoride ions help in making teeth enamel harder by converting [3Ca3(PO4)2.Ca(OH)₂] i.e. Hydroxyapatite to [3Ca₃(PO₄)₂.CaF₂] i.e., Fluorapatite (Harder teeth enamel) via the following the reaction

  $\left[3Ca_{3}\left(PO_{4}\right)_2.Ca\left(OH\right)_2\right]+2F^{-} \rightarrow$  $[3Ca_{3}(PO_{4})_{2}.CaF_{2}]$   +  $2OH^{-}$

The compound that does not proudce nitrogen gas by the thermal decomposition is

Answer:

Explanation:

The thermal decomposition of given compounds is shown below

(NH₄)₂Cr₂O₇    $\underrightarrow{\triangle}$    N₂   +   4H₂O  +   Cr₂O₃

NH₄NO₂   $\underrightarrow{\triangle}$      N₂    +   2H₂O

(NH₄)₂SO₄   $\underrightarrow{\triangle}$   2NH₃    +    H₂SO₄

Ba(N₃)₂   $\rightarrow$    Ba   +  2N₂

Thus, only (NH4)₂SO₄ does not gives N₂ on heating (It gives NH₃). While the rest of the given compounds gives N₂ on their thermal decomposition.

Which of the following salts is the most basic in aqueous solution?

Answer:

Explanation:

Among the give salts

FeCl₃ is acidic in nature i.e., have an acidic solution as it is the salt of a weak base and strong acid.

Al(CN)₃ and Pb(CH₃COO)₂ are the salts of a weak acid and weak base.

CH₃COOK is the salt of a strong base and weak acid.

Hence, the solution of CH₃COOK will be most basic because of the following reaction.

CH₃COOK  +   H₂O     $\rightleftharpoons$       CH₃COOH (Weak acid)  +  KOH  (Strong base)

Which of the following compounds contain(s) no covalent bond(s)?

KCl,PH₃,O₂,B₂H₆,H₂SO₄

Answer:

Explanation:

KCl is the only ionic compund. The structure of PH₃, O₂, B₂H₆ and H₂SO₄ are given below

• Chemistry (2018) - Solved questions (2018)