Bohr's Model of a Hydrogen Atom

Q.

Calculate the weight of CO having the same number of oxygen atoms as are present in 22g of $C{O}_2$

Q.

What is the number of moles of Oxygen atom in 126 amu of $HNO{}_3$

Q.

Two oxides of metal contain 50% and 40% of metal M respectively, if the formula of the first oxide is MO_{​​​​​2}, the formula of the second oxide is?

Q.

What transition in the hydrogen spectrum would have the same wavelength as the Balmer transition n = 4 to n = 2 of $H{e}^{+}$ spectrum?

Q. In which of the following transition will the wavelength be minimum:

1. $\text{n =4 to n =2}$
2. $\text{n =3 to n =1}$
3. $\text{n =6 to n =4}$
4. $\text{n =2 to n =1}$

Q. If the radius of $2^{nd}$ Bohr orbit of hydrogen atom is $r_2$, then the radius of the third Bohr orbit will be:

1. $\frac{4}{9}{r}_2$
2. $4r_2$
3. $\frac{9}{4}{r}_2$
4. $9r_2$

Q. The ionisation energy of hydrogen atom is 13.6 eV. What will be the ionisation energy of $L{i}^{2+}$ ion?

Q.

What are the frequency and wavelength of a photon emitted during a transition from n = 5 state to the n = 2 state in the hydrogen atom ?

1. 4.35×1016 Hz, 691 nm
2. 6.91×1014 Hz, 434 nm
3. 4.35×1015 Hz, 450 nm
4. 6.91×1013 Hz, 400 nm

Q.

Calculate the mass of Na_{​​​​​2}​CO_​​3 which will have the same number of molecules as contained in 12.3 gram of MgSO_​​​4​​MgSO4.7H₂O

Q. The radius of which of the following orbits is the same as that of the first Bohr's orbit of hydrogen atom?

1. $L{i}^{2+}(n=2)$
2. $H{e}^{+}(n=2)$
3. $L{i}^{2+}(n=3)$
4. $B{e}^{3+}(n=2)$

Q. What is the ratio of time periods in the second orbit of the hydrogen atom $\left(T_H\right)$ to the fourth orbit of $H{e}^{+}$ ion $\left(T_{He}\right)$?

1. $1:2$
2. $2:1$
3. $1:4$
4. $4:1$

Q.

The energy associated with the first orbit in the hydrogen atom is –2.18 × ${10}^{–18}$ J $ato{m}^{–1}$ . What is the energy associated with the fifth orbit?

Calculate the radius of Bohr’s fifth orbit for hydrogen atom.

Q. The energy of second Bohr orbit of the hydrogen atom is $-328{\text{kJ mol}}^{-1}$; hence the energy of fourth Bohr orbit would be

1. $-41{\text{kJ mol}}^{-1}$
2. $-1312{\text{kJ mol}}^{-1}$
3. $-164{\text{kJ mol}}^{-1}$
4. $-82{\text{kJ mol}}^{-1}$

Q. Calculate the ratio of the speed of light and the speed of electron in the first Bohr orbit of a hydrogen atom.

1. 138
2. 139
3. 137
4. 140

Q.

In an organic compound of molar mass 108 gram/mole C, H, and N atoms are present in 9:1:3.5 by weight find out the molecular formula of the compound

Q. If the ionisation energy for H atom is $13.6eV$, calculate the required energy in eV to excite it from the ground state to the first excited state.

1. $13.6eV$
2. $3.4eV$
3. $10.2eV$
4. $12.75eV$

Q. The ratio of the radii of the $2^{nd}$ Bohr orbit of hydrogen atom to $3^{rd}$ Bohr orbits of $L{i}^{2+}$ is:

1. $3:2$
2. $2:3$
3. $4:3$
4. $3:4$

Q.

From a sample of 196g of H2SO4 if all the oxygen and hydrogen atoms are removed and converted to H2O. Find the max. mole of H2O formed.

Q.

A compound contains c=34.6percent , H=3.85 percent, andO=61.55percent .Calculate the empirical formula

Q. The frequency of light emitted for the transition $n=4$ to $n=2$ of $H{e}^{+}$ is equal to the transition in $H$-atom corresponding to which of the following:

1. $n=3$ to $n=1$
2. $n=2$ to $n=1$
3. $n=3$ to $n=2$
4. $n=4$ to $n=3$

Q. Calculate the energy of the photon emitted during the transition from energy levels n = 4 to n = 2 in a hydrogen atom.

1. $4.09\times {10}^{-19}J$
2. $2.42\times {10}^{-19}J$
3. $5.42\times {10}^{-19}J$
4. $3.42\times {10}^{-19}J$

Q. Which hydrogen like species will have the same radius as that of Bohr's first orbit of hydrogen atom?

1. $n=3,L{i}^{2+}$
2. $n=2,H{e}^{+}$
3. $n=2,B{e}^{3+}$
4. $n=2,L{i}^{3+}$

Q. How many times does the electron go around the first orbit of hydrogen atom in one second?

1. $13.18\times {10}^{15}$
2. $6.59\times {10}^{13}$
3. $2.07\times {10}^{13}$
4. $6.59\times {10}^{15}$

Q.

Two elements${\mathrm{XY}}_2$ X atomic weight 75 and Y atomic weight 16 combine to give compound having 75.8% of X. The formula of the compound is

Q. According to Bohr's theory, the energy of an electron in the $n^{th}$ energy level of hydrogen like species is given by:
$E_n=\frac{-21.76\times {10}^{-19}}{n^2}\left(Z^2\right)J$
Calculate the longest wavelength of light that will be needed to completely remove an electron from the third Bohr orbit of $H{e}^{+}$ ion.

1. $2055\stackrel{\circ }{\text{A}}$
2. $205.5\stackrel{\circ }{\text{A}}$
3. $2.055\stackrel{\circ }{\text{A}}$
4. $20.55\stackrel{\circ }{\text{A}}$

Q. Energy of an electron is given by
$E=-2.178\times {10}^{-18}J\left(\frac{Z^2}{n^2}\right)$ wavelength of light required to excite an electron in an hydrogen atom from level n = 1 to n = 2 will be
$(h=6.62\times {10}^{-34}Jsandc=3.0\times {10}^{8}m{s}^{-1})$

1. $6.500\times {10}^{-7}m$
2. $1.214\times {10}^{-7}m$
3. $8.500\times {10}^{-7}m$
4. $2.816\times {10}^{-7}m$

Q. The energy of second Bohr orbit of the hydrogen atom is $-328{\text{kJ mol}}^{-1}$; hence the energy of fourth Bohr orbit would be

1. $-41{\text{kJ mol}}^{-1}$
2. $-1312{\text{kJ mol}}^{-1}$
3. $-164{\text{kJ mol}}^{-1}$
4. $-82{\text{kJ mol}}^{-1}$

Q.

A compound has the molecular formula $X_4{O}_6$ . If 11 g of $X_4{O}_6$ has 6.2 g of X, then what is the atomic mass of X?

Q. Find the number of waves made by a Bohr electron in one complete revolution in the $3^{rd}$ orbit.

Q. Find the ratio of the difference in energy between the first and the second Bohr's orbit to that between the second and third Bohr's orbit of a hydrogen atom.

1. $\frac{1}{3}$
2. $\frac{4}{9}$
3. $\frac{1}{2}$
4. $\frac{27}{5}$