Tag: chemistry

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Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

Electronic configuration of silver atom in ground state.

  1. $\left[ Kr \right] { 3d }^{ 10 }{ 4s }^{ 1 }$
  2. $\left[ Xe \right] { 4f }^{ 14 }{ 5d }^{ 10 }{ 6s }^{ 1 }$
  3. $\left[ Kr \right] { 4d }^{ 10 }{ 5s }^{ 1 }$
  4. $\left[ Kr \right] { 4d }^{ 9 }{ 5s }^{ 2 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The electronic configuration of $Ag$ in ground state is:$[Kr]4d^{10}5s^1$

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

Fill in the blanks 
Zero group elements are known as _________.

  1. chalcogen

  2. inert gases

  3. halogens

  4. alkali metals
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The $'0'$ group elements have complete octate in outermost shell. As a result they have stable configuration due to which, they do not react with other elements. Hence they are known as inert gases.

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

An element $X$ belongs to fourth period and fifteenth group of the periodic table. Which of the following statements is true?

  1. It has a completely filled s-orbital and a partially filled d-orbital.

  2. It has completely filled s-and p-orbitals and a partially filled d-orbital.

  3. It has completely filled s-and p-orbitals and a half-filled d-orbital.

  4. It has a half-filled p-orbital and completely filled s-and d-orbitals.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Group 15 has a valence shell electronic configuration of $ns^2np^5$ and period $=4$$ means its $n=4$

thus electronic configuration of element $X$  is $4s^24p^3$

Elements of Group 15 and period 2 onwards are: $N, P, As, Sb, Bi$

Thus $X$ is Arsenic ($As$) and has electronic configuration of: $1s^22s^22p^63s^23p^63d^{10}4s^24p^3$. 

Thus, $s$ and $d-$orbitals are fully-filled and $p-$orbital is half-filled.

Hence, the correct option is $\text{D}$
Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

Which of the following is an artificial element made by man?

  1. Gallium

  2. Iron

  3. Helium

  4. Americium
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
In chemistry, a synthetic element is a chemical element that does not occur naturally on Earth, and can only be created artificially. So far, 24 synthetic elements have been created (those with atomic numbers 95–118). Americium is one of them having atomic no. 95.

Hence, the answer is option $D$.
Multiple choice chemistry hydroxy compounds and ethers physical properties of ethers ethers alcohols, phenols and ethers

Ethers have lower boiling points than their corresponding isomeric alcohols because of?

  1. hydrogen bonding in alcohols that is absent in ethers due to low polarity

  2. hydrogen bonding in ethers due to high polarity

  3. insolubility of ethers in water due to less polarity

  4. inertness of ethers as compared to alcohols.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ethers ROR cannot form intermolecular Hydrogen bond due to the absence of H attached with the electronegative atom as N/O/F, but in case of alcohols, they have -OH which can undergo intermolecular hydrogen bonding and that increases their boiling point.

Thus, Ethers have lower boiling points than their corresponding isomeric alcohols because of hydrogen bonding in alcohols that is absent in ethers due to low polarity.

Multiple choice chemistry hydroxy compounds and ethers physical properties of ethers ethers alcohols, phenols and ethers

Correct order of boiling points among following is: $\underset{(X)}{CH _3(CH _2) _3CH _3}, \,\,\,\,\underset{(Y)}{C _2H _5OC _2H _5},\,\,\,\,\,\,\underset{(Z)}{CH _3(CH _2) _3OH}$

  1. X > Y > Z

  2. Y > X > Z

  3. Z > X > Y

  4. Z > Y > X
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The boiling point of a molecule depends on the strength of intermolecular interaction such as Vandewaal's attraction, hydrogen bonding etc.

Alkanes, such as $\underset{X}{CH _3(CH _2) _3CH _3}$, being non-polar have the weakest force of attraction called dispersion or London forces.
Ethers, such as $\underset{(Y)}{C _{2}H _{5}OC _2H _5}$, have small dipole moment or weakly polar thus have dipole-dipole interaction. This is stronger than the London forces.
Alcohols, such as $\underset{(Z)}{CH _3(CH _2) _3OH}$, are polar molecules, therefore, have strong dipolar interaction. Moreover, they form an intermolecular hydrogen bond that further increases the attraction (association).

Hence the order of their boiling point will be:
$\underset{(Z)}{CH _3(CH _2) _3OH}>\underset{(Y)}{C _{2}H _{5}OC _2H _5}>\underset{X}{CH _3(CH _2) _3CH _3}$

OR $Z>Y>X$