List of practice Questions

(i) Calculate the total number of electrons present in one mole of methane.
(ii) Find (a) the total number and (b) the total mass of neutrons in 7 mg of 14C. (Assume that the mass of a neutron = 1.675 × 10^–27 kg).
(iii) Find (a) the total number and (b) the total mass of protons in 34 mg of NH₃ at STP. Will the answer change if the temperature and pressure are changed?

Describe the theory associated with the radius of an atom as it

gains an electron
loses an electro

How would you react to the statement that the electronegativity of N on Pauling scale is 3.0 in all the nitrogen compounds?

What is the basic difference between the terms electron gain enthalpy and electronegativity?

Define the principal focus of a concave mirror.

Would you expect the second electron gain enthalpy of O as positive, more negative or less negative than the first? Justify your answer.

(i) Calculate the number of electrons which will together weigh one gram.
(ii) Calculate the mass and charge of one mole of electrons.

The following distribution gives the state-wise teacher-student ratio in higher secondary schools of India. Find the mode and mean of this data. Interpret the two measures.

Number of students per teacher	Number of states / U.T
15 - 20	3
20 - 25	8
25 -30	9
30 - 35	10
35 - 40	3
40 - 45	0
45 - 50	0
50 - 55	2

If 10 volumes of dihydrogen gas reacts with five volumes of dioxygen gas, how many volumes of water vapour would be produced?

Dinitrogen and dihydrogen react with each other to produce ammonia according to the following chemical equation: \(N_2 (g) + H_2 (g) → 2NH_3 (g)\)

Calculate the mass of ammonia produced if 2.00 × 10³g dinitrogen reacts with 1.00 × 10³ g of dihydrogen.
Will any of the two reactants remain unreacted?
If yes, which one and what would be its mass?

Which of the following pairs of elements would have a more negative electron gain enthalpy?

O or F
F or Cl

What are the various factors due to which the ionization enthalpy of the main group elements tends to decrease down a group?

How would you explain the fact that the first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium?

In a reaction \(A + B_2 → AB_2\) Identify the limiting reagent, if any, in the following reaction mixtures.

300 atoms of A + 200 molecules of B
2 mol A + 3 mol B
100 atoms of A + 100 molecules of B
5 mol A + 2.5 mol B
2.5 mol A + 5 mol B

Among the second period elements the actual ionization enthalpies are in the order
Li < B < Be < C < O < N < F < Ne.
Explain why

Be has higher Δ_iH than B
O has lower Δ_iH than N and F?

Energy of an electron in the ground state of the hydrogen atom is -2.18 x 10^-18 J. Calculate the ionization enthalpy of atomic hydrogen in terms of J mol^-1 .

If the speed of light is 3.0×10⁸ ms^–1, calculate the distance covered by light in 2.00 ns.

The following data gives the distribution of total monthly household expenditure of 200 families of a village. Find the modal monthly expenditure of the families. Also, find the mean monthly expenditure :

Expenditure (in Rs)	Number of families
1000 - 1500	24
1500 - 2000	40
2000 - 2500	33
2500 - 3000	28
3000 - 3500	30
3500 - 4000	22
4000 - 4500	16
4500 - 5000	7

What is the significance of the terms - 'isolated gaseous atom' and 'ground state' while defining the ionization enthalpy and electron gain enthalpy?
Hint: Requirements for comparison purposes.

A copper wire has diameter 0.5 mm and resistivity of \(1.6×10^{–8} \ Ω m\). What will be the length of this wire to make its resistance 10 Ω? How much does the resistance change if the diameter is doubled?

The size of isoelectronic species - F^-, Ne and Na⁺is affected by