Class 11th

14.34. What is the full form of PCBs and what are they?

3.35. Anything that influences the valence electrons will affect the chemistry of the element. Which one of the following factors does not affect the valence shell?

(a) Valence principal quantum number (n)

(b) Nuclear charge (Z)

(c) Nuclear mass

(d) Number of core electrons

3.34. Which of the following statements related to the modem periodic table is incorrect?

(a) The p-block has 6 columns, because a maximum of 6 electrons can occupy all the orbitals in a p-subshell.

(b) The d-block has 8 columns, because a maximum of 8 electrons can occupy all the orbitals in a d-subshell.

(c) Each block contains a number of columns equal to the number of electrons that can occupy that subshell.

(d) The block indicates value of azimuthal quantum number (l) for the last subshell that received electrons in building up the electronic configuration.

14.34. Ozone depletion is mainly due to

14.2. BOD is a measure of

3.33. In the modern periodic table, the period indicates the value of

(a) Atomic number

(b) Mass number

(c) Principal quantum number

(d) Azimuthal quantum number?

3.32. Predict the formulas of the stable binary compounds that would be formed by the combination of the following pairs of elements:

(a) Lithium and oxygen             

(b) Magnesium and nitrogen

(c) Aluminium and iodine         

(d) Silicon and oxygen

(e) Phosphorous and fluorine   

(f) Element 71 and fluorine.

Questions and Answers:

14.1. Which acid is most abundant in acid rain?

14.5. Photochemical smog occurs in

(a) Warm, dry and sunny climate (b) cool (c) humid (d) none of the above.

14.29 Read the following statements carefully. Select the incorrect statement.

(a) Besides carbon dioxide, other greenhouse gases are methane, water vapour, nitrous oxide, CFCs and ozone.

(b) Methane is produced naturally when vegetation is burnt, digested or rotted in the absence of oxygen.

(c) Large amounts of methane are released in paddy fields, coal mines, from rotting garbage dumps and by fossil fuels.

(d) Methane are man-made industrial chemicals used in air conditioning etc.