List of top Chemistry Questions

Calculate:

1. ∆G^Θ and 
2. the equilibrium constant for the formation of NO₂ from NO and O₂ at 298 K

\(NO (g) + \frac 12O_2 (g) ⇋ NO_2 (g)\)
where,
 ∆_fG^Θ (NO₂) = 52.0 kJ/mol
∆_fG^Θ (NO) = 87.0 kJ/mol
∆_fG^Θ (O₂) = 0 kJ/mol.

How do you account for the formation of ethane during chlorination of methane?

At 1127 K and 1 atm pressure, a gaseous mixture of CO and CO₂ in equilibrium with soild carbon has 90.55% CO by mass
\(C(s) + CO_2(g) ⇋ 2CO(g)\)
Calculate K_c for this reaction at the above temperature.

Bromine monochloride, BrCl decomposes into bromine and chlorine and reaches the equilibrium:
\(2BrCl (g) ⇋ Br_2 (g) + Cl_2 (g)\)
for which K_c = 32 at 500 K. If initially pure BrCl is present at a concentration of 3.3 × 10^–3 mol L^–1, what is its molar concentration in the mixture at equilibrium?

What is meant by the term bond order? Calculate the bond order of: \(N_2\), \(O_2\), \(O_2^+\) and \(O_2^-\) .

Equilibrium constant, K_c for the reaction
\(N_2 (g) + 3H_2 (g) ⇋ 2NH_3 (g)\)
At 500 K is 0.061 At a particular time, the analysis shows that composition of the reaction mixture is 3.0 mol L^–1 N₂, 2.0 mol L^–1 H₂ and 0.5 mol L^–1 NH₃. Is the reaction at equilibrium? If not in which direction does the reaction tend to proceed to reach equilibrium?

One of the reaction that takes place in producing steel from iron ore is the reduction of iron(II) oxide by carbon monoxide to give iron metal and CO₂.
\(FeO (s) + CO (g) ⇋ Fe (s) + CO_2 (g);\ K_p = 0.265\  \text {atm}\) at 1050 K
What are the equilibrium partial pressures of CO and CO₂ at 1050 K if the initial partial pressures are: \(P_{CO}\) = 1.4 atm and \(P_{CO_2}\) = 0.80 atm?

(a) How many subshells are associated with n = 4 ? (b) How many electrons will be present in the subshells having ms value of \(-\frac{1}{2}\) for n = 4 ?

Indicate the number of unpaired electrons in : (a) P, (b) Si, (c) Cr, (d) Fe and (e) Kr.

Define hydrogen bond. Is it weaker or stronger than the van der Waals forces?

The unpaired electrons in Al and Si are present in 3p orbital. Which electrons will experience more effective nuclear charge from the nucleus ?

Describe the hybridisation in case of \( PCl_5\). Why are the axial bonds longer as compared to equatorial bonds?

Among the following pairs of orbitals which orbital will experience the larger effective nuclear charge? 
(i) 2s and 3s 
(ii) 4d and 4f 
(iii) 3d and 3p

The bromine atom possesses 35 electrons. It contains 6 electrons in 2p orbital, 6 electrons in 3p orbital and 5 electron in 4p orbital. Which of these electron experiences the lowest effective nuclear charge ?

The quantum numbers of six electrons are given below. Arrange them in order of increasing energy. If any of these combination(s) has/have the same energy lists: 
1. n = 4, l = 2, ml = –2 , ms = \(-\frac{1}{2}\)
2. n = 3, l = 2, ml = 1 , ms = \(+\frac{1}{2}\)
3. n = 4, l = 1, ml = 0 , ms = \(+\frac{1}{2}\)
4. n = 3, l = 2, ml = –2 , ms = \(-\frac{1}{2}\)
5. n = 3, l = 1, ml = –1 , ms = \(+\frac{1}{2}\) 
6. n = 4, l = 1, ml = 0 , ms = \(+\frac{1}{2}\)

Compare the relative stability of the following species and indicate theirmagnetic properties; \(O_2\), \(O^+_2\), \(O_2^-\) (superoxide), \(O_2^{2-}\)(peroxide)

If the electron's position is measured within an accuracy of + 0.002 nm, calculate the uncertainty in the electron's momentum. Suppose the momentum of the electron is \(\frac{h}{4\pi m}\) × 0.05 nm, is there any problem in defining this value?

The velocity associated with a proton moving in a potential difference of 1000 V is 4.37×10⁵ ms^–1. If the hockey ball of mass 0.1 kg is moving with this velocity, calculate the wavelength associated with this velocity.

Use molecular orbital theory to explain why the \(Be_2\) molecule does not exist.

Explain the formation of \(H_2\) molecule on the basis of valence bond theory.

Distinguish between a sigma and a pi bond.

If the velocity of the electron in Bohr’s first orbit is 2.19×10⁶ms^–1, calculate the de Broglie wavelength associated with it.

What do you understand by bond pairs and lone pairs of electrons? Illustrate by giving one example of each type.

Which hybrid orbitals are used by carbon atoms in the following molecules? 

1. \(CH_3-CH_3\); 
2. \(CH_3-CH=CH_2\); 
3. \(CH_3-CH_2-OH\); 
4. \(CH_3-CHO\) 
5. \(CH_3COOH\)

Similar to electron diffraction, a neutron diffraction microscope is also used for the determination of the structure of molecules. If the wavelength used here is 800 pm, calculate the characteristic velocity associated with the neutron.