MCQ
Which element is named after the name of a planet is ?
- A$Hg$
- B$Po$
- ✓$Pu$
- D$Ra$
Ceres $(1801)=$ Cerium (1803)
Pallas $(1802)=$ Palladium (1803)
Neptune $(1846)=$ Neptunium (1940)
Pluto $(1930)=$ Plutonium (1940)
All were named after large solar system bodies, which, at the time the elements were named, the corresponding celestial bodies were considered to be planets. After discovering many more asteroids, Ceres and Pallas were demoted to asteroids in the asteroid belt. Pluto was also demoted, much more recently, to a dwarf planet, which also resulted in Ceres being 'promoted' to dwarf planet status! Pallas is too small to be considered a dwarf planet, so it is still considered an asteroid. Obviously Uranus and Neptune are considered planets, being the $4^{th}$ and $5^{th}$ largest bodies in the solar system. Mercury is the name for a planet and an element, but as Daniel Spector mentioned in his answer, they are both named after a god, rather than the element being specifically named after the planet.
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Assertion $(A)$ : $\mathrm{S}_{\mathrm{N}} 2$ reaction of $\mathrm{C}_6 \mathrm{H}_5 \mathrm{CH}_2 \mathrm{Br}$ occurs more readily than the $\mathrm{S}_{\mathrm{N}} 2$ reaction of $\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{Br}$.
Reason $(R)$ : The partially bonded unhybridized p-orbital that develops in the trigonal bipyramidal transition state is stabilized by conjugation with the phenyl ring.
In the light of the above statements, choose the most appropriate answer from the options given below:
Neglect any changes in volume
| $LIST-I$ | $LIST-II$ |
| $P(10 \ mL $ of $0.1 M NaOH +20 \ mL$ of $0.1 M $ acetic acid$)$ diluted to $60 \ mL$ | $1$ the value of $\left[ H ^{+}\right]$ does not change on dilution |
| $Q (20 \ mL $ of $ 0.1 \ M \ NaOH +20 \ mL $ of $0.1 \ M $ acetic acid$)$ diluted to $ 80\ mL$ | $2$ the value of $\left[ H ^{+}\right]$ changes to half of its initial value on dilution the value of $\left[ H ^{+}\right]$ changes to two times of its initial value on dilution |
| $R(20 \ mL $ of $ 0.1 \ M HCl +20 \ mL$ of $0.1 \ M$ ammonia solution$)$ diluted to $80 \ mL$ | $3$ the value of $\left[ H ^{+}\right]$changes to $1 / \sqrt{2}$ times of its initial value on dilution |
| $S10 \ mL$ saturated solution of Ni $( OH )_2$ in equilibrium with excess solid Ni $( OH )_2$ s diluted to $20 \ mL ($solid Ni $( OH )_2$ is still present afterdilution$).$ |
$4$the value of $\left[ H ^{+}\right]$changes to $\sqrt{2}$ times of its initial value on dilution |
| $5$ the value of $\left[ H ^{+}\right]$changes to $\sqrt{2}$ times of its initial value on dilution |