Structure of Atom Test

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Structure of Atom Test - 46

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Weekly Quiz Competition

Question 1
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Study the following table.
Compound (mol. mass) Compound Mass of the (in grams) taken
I. $$CO_2(44)$$ 4.4
II. $$NO_2(46)$$ 2.3
III. $$H_2O_2(34)$$ 6.8
IV. $$SO_2(64)$$ 1.6

Which two compounds have least mass of oxygen?
(Molecular masses of compounds are given in brackets)

A
II and IV

B
I and III

C
I and II

D
III and IV

Solution

I. Mass of oxygen present $$=\dfrac{4.4}{44}\times 32 = 3.2\,g$$
II. Mass of oxygen present $$= \dfrac{2.3}{46}\times 32= 1.6\,g$$
III. Mass of oxygen present $$= \dfrac{6.8}{34} \times 32= 6.4\,g$$
IV. Mass of oxygen present$$= \dfrac{1.6}{64}\times 32 = 0.8\,g$$
$$\therefore $$ II and IV have least mass of oxygen.
Question 2
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What is ratio of time periods $$\left( { { T }_{ 1 } }/{ { T }_{ 2 } } \right) $$ in second orbit of hydrogen atom to third orbit of $${He}^{+}$$ ion?

A
$$\dfrac { 8 }{ 27 } $$

B
$$\dfrac { 32 }{ 27 } $$

C
$$\dfrac { 27 }{ 32 } $$

D
$$\dfrac { 27 }{ 8 } $$

Solution

we know that
time period$$\propto \cfrac { { n }^{ 3 } }{ { t }^{ 2 } }$$
n=energy level
t=z=valan enly
$$\cfrac { { T }_{ H } }{ { T }_{ He } } =\cfrac { { n }_{ 1 }^{ 3 }{ t }_{ 2 }^{ 2 } }{ { n }_{ 2 }^{ 3 }{ t }_{ 1 }^{ 2 } } $$
=$$\cfrac { \left( 8 \right) \times \left( 4 \right) }{ \left( 27 \right) \times \left( 1 \right) } $$
ratio=$$\cfrac { 32 }{ 17 } $$
Question 3
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$$0.25 g$$ of an element $$M$$ reacts with excess fluorine to produce $$0.547 g$$ of the hexafluoride $$MF_6$$. What is the element?

A
$$Cr$$

B
$$Mo$$

C
$$S$$

D
$$Te$$

Solution

We have

$$M + F_2 \rightarrow MF_6$$

moles of M = moles of $$MF_6$$

let mass of element M = $$x g$$

therefore we have

$$\dfrac{0.25}{x} = \dfrac{0.547}{x+114}$$

so, solving we get , $$x = 95.9 g$$

therefore, the elemnt is $$Mo$$
Question 4
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Which of the following pairs is correctly matched ?

A
Experimental observation - (a) X-ray spectra

Phenomenon - Charge on the nucleus

B
Experimental observation - (b) a- particle scattering

Phenomenon - Quantized electron orbit

C
Experimental observation - (c) Emission spectra

Phenomenon - Quantization of energy

D
Experimental observation - (d) The photoelectric effect

Phenomenon - The nuclear atom

Solution

The high speed electrons go into the interior of the atoms of the target material and are attracted by the positive charge on their Nuclei. As an electron passes lose to the positive nucleus of an atom in the target the electron is deflected from its path as shown in fig. This result in deceleration of the electron.
The loss in energy of the electron during deceleration is emitted in the form of X-rays.
Question 5
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Which of the following sets of quanta numbers could represent the last electron added to complete the electronic configuration for a ground state atom of Br (Z = 35)?

A
$$4, 0, 0, - \cfrac {1}{2}$$

B
$$4, 1, 1, - \cfrac {1}{2}$$

C
$$3, 1, 1, - \cfrac {1}{2}$$

D
$$4, 1, 2, + \cfrac {1}{2}$$

Solution

The valence node shell configuration is $$4s^2\,\, 4p^5$$ for the last electron $$n=4, l=1$$.

$$m=-1, 0$$ or $$ +1, s=+\cfrac {1}{2}$$ or $$-\cfrac {1}{2}$$.

Hence, $$ 4, 1, 1, -\cfrac {1}{2}$$

Therefore, option B is correct.
Question 6
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Arrangement of the following group of orbitals in which they fill with electrons :
(5f, 6p, 4p, 6s, 4d, 4f )

A
$$4p, 4d, 6s, 4f, 6p, 5f$$

B
$$6s, 4d, 4f, 5f, 4p, 6p $$

C
$$6s, 4p, 4d, 4f, 5f, 6p$$

D
$$4d, 4p, 4f, 5f, 6s, 6p$$

Solution

Electrons will first fill orbitals by the sum of the quantum numbers n and l. Orbitals with equal values of (n+l) will fill with the lower n values first.
So energies of $$4p, 4d, 6s, 4f, 6p, 5f$$ are 5,6,6,7,7,8 respectively.
Hence option A is correct.
Question 7
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A compound has the molecular formula $$X_4O_6$$. If $$10$$ g of $$X_4O_6$$ has $$5.72$$ g X, then the atomic mass of X is :

A
$$32$$ amu

B
$$64$$ amu

C
$$67$$ amu

D
$$98$$ amu

Solution

Molecular weight of $$X_4O_6=(4a+96)$$

$$\because (4a+96)g$$ $$ X_4O_6$$ contains $$X=4a$$ g

$$\therefore 10$$g of $$X_4O_6$$ contains X$$=\displaystyle\frac{4a\times 10}{4a+96}$$

$$5.72=\displaystyle\frac{4a\times 10}{4a+96}$$

$$22.88a+549.12=40a$$

$$17.12a=549.12$$

$$a=32.07$$amu.
Question 8
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According to the Bohr's atomic model, the relation between principal quantum number (n) and radius of orbit(r) is?

A
$$r\propto n^2$$

B
$$r\propto \displaystyle\frac{1}{n^2}$$

C
$$r\propto \displaystyle \frac{1}{n}$$

D
$$r\propto n$$

Solution

Electron angular momentum about the nucleus is an integer multiple of $$\displaystyle\frac{h}{2\pi}$$, where h is Planck's constant.
Thus, $$I\omega =mvr=\displaystyle \frac{nh}{2\pi}$$
Hence $$r\propto n$$.
Question 9
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What does the electronic configuration $$1{ s }^{ 2 },2{ s }^{ 2 },2{ p }^{ 5 },3{ s }^{ 1 }$$ indicate?

A
Ground state of fluorine

B
Excited state of fluorine

C
Excited state of neon

D
Excited state of the $${ O }_{ 2 }^{ - }$$ ion

Solution

The atomic number of Neon is $$10$$
G.S $$Ne\left[ 10 \right] :1{ s }^{ 2 },2{ s }^{ 2 },2{ p }^{ 5 }\quad $$
E.S $$Ne\left[ 10 \right] :1{ s }^{ 2 },2{ s }^{ 2 },2{ p }^{ 5 },3{ s }^{ 1 }\quad $$
Hence $$1{ s }^{ 2 },2{ s }^{ 2 },2{ p }^{ 5 },3{ s }^{ 1 }$$ electronic configuration indicates the excited state of neon
Question 10
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The ratio of kinetic energy and the total energy of the electron in the nth quantum state of Bohr's atomic model of hydrogen atom is

A
$$-2$$

B
$$-1$$

C
$$+2$$

D
$$+1$$

Solution

The kinetic energy of the electron in the nth state
$$K=\dfrac {mZ^2e^4}{8\varepsilon ^2_0h^2n^2}$$
The total energy of the electron in the nth state
$$T=\dfrac {-mZ^2e^4}{8\varepsilon ^2_0h^2n^2}$$
$$\therefore \dfrac {K}{T}=-1$$

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	Compound (mol. mass)	Compound Mass of the (in grams) taken
I.	$$CO_2(44)$$	4.4
II.	$$NO_2(46)$$	2.3
III.	$$H_2O_2(34)$$	6.8
IV.	$$SO_2(64)$$	1.6

Structure of Atom Test - 46

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Structure of Atom Test - 46

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Question 1

II and IV

I and III

I and II

III and IV

Solution

Question 2

$$\dfrac { 8 }{ 27 } $$

$$\dfrac { 32 }{ 27 } $$

$$\dfrac { 27 }{ 32 } $$

$$\dfrac { 27 }{ 8 } $$

Solution

Question 3

$$Cr$$

$$Mo$$

$$S$$

$$Te$$

Solution

Question 4

Experimental observation - (a) X-ray spectra Phenomenon - Charge on the nucleus

Experimental observation - (b) a- particle scattering Phenomenon - Quantized electron orbit

Experimental observation - (c) Emission spectra Phenomenon - Quantization of energy

Experimental observation - (d) The photoelectric effectPhenomenon - The nuclear atom

Solution

Question 5

$$4, 0, 0, - \cfrac {1}{2}$$

$$4, 1, 1, - \cfrac {1}{2}$$

$$3, 1, 1, - \cfrac {1}{2}$$

$$4, 1, 2, + \cfrac {1}{2}$$

Solution

Question 6

$$4p, 4d, 6s, 4f, 6p, 5f$$

$$6s, 4d, 4f, 5f, 4p, 6p $$

$$6s, 4p, 4d, 4f, 5f, 6p$$

$$4d, 4p, 4f, 5f, 6s, 6p$$

Solution

Question 7

$$32$$ amu

$$64$$ amu

$$67$$ amu

$$98$$ amu

Solution

Question 8

$$r\propto n^2$$

$$r\propto \displaystyle\frac{1}{n^2}$$

$$r\propto \displaystyle \frac{1}{n}$$

$$r\propto n$$

Solution

Question 9

Ground state of fluorine

Excited state of fluorine

Excited state of neon

Excited state of the $${ O }_{ 2 }^{ - }$$ ion

Solution

Question 10

$$-2$$

$$-1$$

$$+2$$

$$+1$$

Solution

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Experimental observation - (a) X-ray spectra

Phenomenon - Charge on the nucleus

Experimental observation - (b) a- particle scattering

Phenomenon - Quantized electron orbit

Experimental observation - (c) Emission spectra

Phenomenon - Quantization of energy

Experimental observation - (d) The photoelectric effect

Phenomenon - The nuclear atom