Science (English Medium) Class 11 - CBSE Question Bank Solutions

How is an excessive content of CO₂ responsible for global warming?

Give one method for industrial preparation and one for laboratory preparation of CO₂.

Which electron displacement effect explains the following correct orders of acidity of the carboxylic acids?

\[\ce{CH3CH2COOH > (CH3)2CHCOOH > (CH3)3C.COOH}\]

Give one method for industrial preparation and one for laboratory preparation of CO.

Which electron displacement effect explains the following correct orders of acidity of the carboxylic acids?

\[\ce{Cl3CCOOH > Cl2CHCOOH > ClCH2COOH}\]

The number of atoms present in one mole of an element is equal to Avogadro number. Which of the following element contains the greatest number of atoms?

The Balmer series in the hydrogen spectrum corresponds to the transition from n₁ = 2 to n₂ = 3, 4,.......... This series lies in the visible region. Calculate the wave number of line associated with the transition in Balmer series when the electron moves to n = 4 orbit. (R_H = 109677 cm^–1)

Chlorophyll present in green leaves of plants absorbs light at 4.620 × 10¹⁴ Hz. Calculate the wavelength of radiation in nanometer. Which part of the electromagnetic spectrum does it belong to?

Assertion (A): Black body is an ideal body that emits and absorbs radiations of all frequencies.

Reason (R): The frequency of radiation emitted by a body goes from a lower frequency to higher frequency with an increase in temperature.

Threshold frequency, ν₀ is the minimum frequency which a photon must possess to eject an electron from a metal. It is different for different metals. When a photon of frequency 1.0 × 10¹⁵ s^–1 was allowed to hit a metal surface, an electron having 1.988 × 10^–19 J of kinetic energy was emitted. Calculate the threshold frequency of this metal. Show that an electron will not be emitted if a photon with a wavelength equal to 600 nm hits the metal surface.

Those elements impart colour to the flame on heating in it, the atoms of which require low energy for the ionisation (i.e., absorb energy in the visible region of spectrum). The elements of which of the following groups will impart colour to the flame?

(i) 2

(ii) 13

(iii) 1

(iv) 17

Among the elements \[\ce{B, Al, C}\] and \[\ce{Si}\], which element has the highest first ionisation enthalpy? 

Nitrogen has positive electron gain enthalpy whereas oxygen has negative. However, oxygen has lower ionisation enthalpy than nitrogen. Explain.

Arrange the elements \[\ce{N, P, O}\] and \[\ce{S}\] in the order of increasing first ionisation enthalpy. Give reason for the arrangement assigned.

Explain the deviation in ionisation enthalpy of some elements from the general trend by using the given figure.

Explain the following:

Ionisation enthalpy decrease in a group from top to bottom?

Assertion (A): Generally, ionisation enthalpy increases from left to right in a period.

Reason (R): When successive electrons are added to the orbitals in the same principal quantum level, the shielding effect of inner core of electrons does not increase very much to compensate for the increased attraction of the electron to the nucleus.

Define ionisation enthalpy. Discuss the factors affecting ionisation enthalpy of the elements and its trends in the periodic table.

Discuss and compare the trend in ionisation enthalpy of the elements of group1 with those of group17 elements.

Polarity in a molecule and hence the dipole moment depends primarily on electronegativity of the constituent atoms and shape of a molecule. Which of the following has the highest dipole moment?