Structure of Atom Test

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Structure of Atom Test - 57

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following hydrogen bonds are strongest in vapour phase?

A
$$HF.....HF$$

B
$$HF...HCl$$

C
$$HCl...HCl$$

D
$$HF...HI$$

Solution

Hydrogen bond is limited to certain compounds containing N,O or F. I is fair too big and not electronegative enough.The HCl is bond is polar covalent. HCl does have ionic properties and fully dissacociates in water. But the reason that HF does not fully dissacociates in solution because of its hydrogen bonds with water. Hence HF has strong H–bond and exists in a polymeric form in vapour phase.
Question 2
1 / -0

The unfavorable electrochemical reaction among the following is:

A

B

C

D

Solution

chlorine is more electronegative than iodine hence it can displace iodine from KI but reverse is not possible. in 3rd reaction Zn is more reactive because it is above hydrogen in electrochemical series hence it will replace hydrogen.
similar for 2nd reaction.
hence correct option is (A)
Question 3
1 / -0

Bohr's theory can be applied to determine the?

A
electron gain enthalpy of hydrogen atom

B
Electronegativity of $${ Li }^{ 2+ }$$ ion

C
second ionization energy of helium atom

D
first ionization energy of Be atom
Question 4
1 / -0

In a hydrogen atom the force acting on the electron is proportional to :

A
$$n^{4}$$

B
$$n^{-4}$$

C
$$r^{2}$$

D
$$n^{-2}$$

Solution

A hydrogen atom the force acting on the election is proportional to $$r^2$$.
Hence ,option $$C$$ is correct.
Question 5
1 / -0

Which of the atomic number represents s -block elements?

A
7, 15

B
3, 12

C
6, 12

D
9, 17

Solution

The elements in which the last electron enters the outermost s-orbital are called s-block elements.
The s-block elements have two groups ($$1$$ and $$2$$).

Thus, s-block elements include lithium $$(Li)$$ and magnesium $$(Mg).$$

The periodic table shows exactly where these elements are within the s-block.
Question 6
1 / -0

Containers $$X,\ Y$$ and $$Z$$ of the equal volume contain oxygen, neon and methane respectively at the same temperature and pressure. The correct increasing order of their masses is:

A
$$X < Y< Z$$

B
$$Y < Z < X$$

C
$$Z < X < Y$$

D
$$Z < Y < X$$

Solution

$$n = \dfrac{mass}{ molar\ mass}$$
mass = molar mass $$\times n$$ ($$n$$ is constant in this case as temperature , volume and pressure are constant)
mass of oxygen $$= 32 n$$
mass of neon$$ = 19 n$$
mass of methane $$= 16 n$$
so increasing order is oxygen > neon > methane.
Question 7
1 / -0

Ratio of series limit of Brackett and Pfund series of hydrogen ato spectrum is

A
$$\dfrac{1}{4}$$

B
$$\dfrac{4}{9}$$

C
$$\dfrac{9}{16}$$

D
$$\dfrac{16}{25}$$

Solution

$$\begin{array}{c}{\text { Bracket series }} \text { n }_{1}=3, n_{2}=4,5,\ldots \\\dfrac{1}{\text { series limit }}\propto \left[\dfrac{1}{3^{2}}-\dfrac{1}{n_2^2}\right] \\\propto \dfrac{1}{9}\end{array}$$

$$\begin{array}{l}\text { Pfund series } \quad n_{1}=4, n_{2}=5,6,\ldots \\\dfrac{1}{\text { series limit }}\propto \left[\dfrac{1}{4^{2}}-\dfrac{1}{(n_2)^{2}}\right] \propto \dfrac{1}{16} \\\text { Ratio of series limit }=9/16\end{array}$$
Question 8
1 / -0

The radius of $$He^+$$ ion is $$x\ \mathring{A}$$ in its ground state. The radius of $$Li^{2+}$$ ion in the ground state ($$ \mathring{A}$$ ) is:

A
$$\dfrac{2x}{3}$$

B
$$\dfrac{3x}{2}$$

C
$$\dfrac{2}{3x}$$

D
$$\dfrac{3}{2x}$$

Solution

Radius of an orbit $$= 0.529\times \dfrac {n^2}{Z}$$

$$R \propto \dfrac 1Z$$

$$\dfrac{R_1}{R_2} = \dfrac{Z_2}{Z_1}$$

$$\dfrac {x}{R_2} = \dfrac 32$$

$$R_2 = \dfrac{2x}{3}$$

Hence, option A is correct.
Question 9
1 / -0

Identify the incorrect statement among the following:

A
$$4f$$ and $$5f$$ orbitals are equally shielded

B
d-Block elements show irregular and erractic chemical properties among themselves.

C
$$La$$ and $$Lu$$ have partially filled d-orbitals and no other partially filled orbitals.

D
The chemistry of various lanthanoids is very similar.

Solution

$$4f$$ orbital is nearer to the nucleus as compared to $$5f$$ orbital. Therefore, shielding of $$4f$$ is more than $$5f$$ orbital. Hence, option (A) is correct.
Question 10
1 / -0

Equivalent electric current created by electron of a H-atom in its ground using Bohr's model is nearly

A
$$2.14\times {10}^{-35}A$$

B
$$4.48\times {10}^{-30}A$$

C
$$24\times {10}^{-30}A$$

D
$$70\times {10}^{-35}A$$

Solution

$$\begin{array}{l}\text { Let, radius of } 1^{\text {St }} \text { orbit Atom be "a_o" } \\\text { velocity of } e^{-} \text { in } 1^{\text {st }} \text { orbit is } v \\\text { Time period, }\left[T=\dfrac{2 \pi \cdot a_{0}}{v}]--(1)\right] \end{array}$$

$$\begin{array}{l}\text { Electric current, } i=\dfrac{q}{T} \\\text { From } \\\qquad i=\dfrac{q v}{2 \pi a_{0}}\end{array}$$

$$\begin{array}{l}\text { By keeping approximate experimental } \\\text { values in above expression, we get } \\\qquad i=4.489 \times 10^{-30} A\end{array}$$

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Structure of Atom Test - 57

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Structure of Atom Test - 57

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SHARING IS CARING

Question 1

$$HF.....HF$$

$$HF...HCl$$

$$HCl...HCl$$

$$HF...HI$$

Solution

Question 2

Solution

Question 3

electron gain enthalpy of hydrogen atom

Electronegativity of $${ Li }^{ 2+ }$$ ion

second ionization energy of helium atom

first ionization energy of Be atom

Question 4

$$n^{4}$$

$$n^{-4}$$

$$r^{2}$$

$$n^{-2}$$

Solution

Question 5

7, 15

3, 12

6, 12

9, 17

Solution

Question 6

$$X < Y< Z$$

$$Y < Z < X$$

$$Z < X < Y$$

$$Z < Y < X$$

Solution

Question 7

$$\dfrac{1}{4}$$

$$\dfrac{4}{9}$$

$$\dfrac{9}{16}$$

$$\dfrac{16}{25}$$

Solution

Question 8

$$\dfrac{2x}{3}$$

$$\dfrac{3x}{2}$$

$$\dfrac{2}{3x}$$

$$\dfrac{3}{2x}$$

Solution

Question 9

$$4f$$ and $$5f$$ orbitals are equally shielded

d-Block elements show irregular and erractic chemical properties among themselves.

$$La$$ and $$Lu$$ have partially filled d-orbitals and no other partially filled orbitals.

The chemistry of various lanthanoids is very similar.

Solution

Question 10

$$2.14\times {10}^{-35}A$$

$$4.48\times {10}^{-30}A$$

$$24\times {10}^{-30}A$$

$$70\times {10}^{-35}A$$

Solution

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