List of top Chemistry Questions

Write down the number of 3d electrons in each of the following ions: Ti²⁺, V²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Fe³⁺, CO²⁺, Ni²⁺ and Cu²⁺ . Indicate how would you expect the five 3d orbitals to be occupied for these hydrated ions (octahedral).

The decomposition of hydrocarbon follows the equation
\(k = (4.5 \times 10^{11} s^{-1})e^{-28000 \ K/T }\)
\(Calculate\ E_a\).

Sucrose decomposes in acid solution into glucose and fructose according to the first order rate law, with \(t_{\frac 12} = 3.00\ hours\). What fraction of sample of sucrose remains after \(8 \ hours\)?

Compare the general characteristics of the first series of the transition metals with those of the second and third series metals in the respective vertical columns. Give special emphasis on the following points:

electronic configurations,
oxidation states,
ionisation enthalpies, and
atomic sizes

Write the electronic configurations of the elements with the atomic numbers 61, 91, 101, and 109.

Compare the chemistry of the actinoids with that of lanthanoids with reference to:

electronic configuration
oxidation states and
chemical reactivity.

Use Hund's rule to derive the electronic configuration of Ce³⁺ ion and calculate its magnetic moment on the basis of 'spin-only' formula.

Which is the last element in the series of the actinoids? Write the electronic configuration of this element. Comment on the possible oxidation state of this element.

The chemistry of the actinoid elements is not so smooth as that of the Lanthanoids. Justify this statement by giving some examples from the oxidation state of these elements.

What are inner transition elements? Decide which of the following atomic numbers are the atomic numbers of the inner transition elements: 29, 59, 74, 95, 102, 104.

Determine the osmotic pressure of a solution prepared by dissolving 25 mg of \(K_2SO_4\) in 2 litre of water at \(25\degree C\), assuming that it is completely dissociated.

Determine the amount of \(CaCl_2 (i = 2.47)\) dissolved in 2.5 litre of water such that its osmotic pressure is 0.75 atm at \(27\degree C\).

What are alloys? Name an important alloy which contains some of the lanthanoid metals. Mention its uses.

The rate constant for the decomposition of \(N_2O_5\) at various temperatures is given below:

T/°C	0	20	40	60	80
10⁵ x k/s^-1	0.0787	1.70	25.7	178	2140

Draw a graph between ln k and \(\frac 1T\) and calculate the values of \(A\) and \(E_a\).
Predict the rate constant at 30 ºC and 50 ºC.

The air is a mixture of a number of gases. The major components are oxygen and nitrogen with approximate proportion of \(20\%\) is to \(79\%\) by volume at 298 K. The water is in equilibrium with air at a pressure of 10 atm. At 298 K if the Henry’s law constants for oxygen and nitrogen at 298 K are \(3.30 × 107 mm\) and \(6.51 × 107 mm\) respectively, calculate the composition of these gases in water

Benzene and toluene form ideal solution over the entire range of composition. The vapour pressure of pure benzene and toluene at 300 K are 50.71 mm Hg and 32.06 mm Hg respectively. Calculate the mole fraction of benzene in vapour phase if 80 g of benzene is mixed with 100 g of toluene.

100 g of liquid A \((molar\, mass\, 140\, g\, mol^{–1})\) was dissolved in 1000 g of liquid B \((molar\, mass\, 180\, g\, mol^{–1})\). The vapour pressure of pure liquid B was found to be 500 torr. Calculate the vapour pressure of pure liquid A and its vapour pressure in the solution if the total vapour pressure of the solution is 475 Torr.

Calculate the number of unpaired electrons in the following gaseous ions: Mn³⁺, Cr³⁺, V³⁺ and Ti³⁺. Which one of these is the most stable in aqueous solution?

Which metal in the first series of transition metals exhibits +1 oxidationstate most frequently and why?

In what way is the electronic configuration of the transition elements different from that of the non-transition elements?

What is lanthanoid contraction? What are the consequences of lanthanoid contraction?

What may be the stable oxidation state of the transition element with the following d electron configurations in the ground state of their atoms : 3d³ ,3d⁵ ,3d⁸ and 3d⁴?

To what extent do the electronic configurations decide the stability of oxidation states in the first series of the transition elements? Illustrate your answer with examples.

Why are Mn²⁺ compounds more stable than Fe²⁺ towards oxidation to their +3 state?

A first order reaction takes 40 min for 30% decomposition. Calculate \(t_{\frac 12}\).