A substance, W has a concentration of 0.02mol when its molar mass was found to be 74.0 gmol-1 . Another substance V contains 1.00x1023 atoms and has molar mass of

40.0gmol-1. Which of the two substances has the greater mass (in grams)? [L =

6.02x1023]

ii) A 250 cm3

solution contains 14.63g of sodium chloride (NaCl). Calculate the

concentration of the solution in moldm-3

[Na= 23, Cl = 35.5]

Explanation:

mass of W in gram  = mole x molecular weight

= .02 x 74 = 1.48 gm

mass of V in gram

first of all we shall calculate the no of moles of V

1 mole = 6.0 x  10²³ atoms

1 x 10²³ atoms = 1 / 6 moles

mass of V in grams

= 40 / 6

= 6.67 grams .

So V has greater mass .

ii )

molecular weight of sodium chloride

= 58.5 gm

14.63 gram of sodium chloride

= 14.63 / 58.5 = .25 moles

250 cm³ = 250 x 10⁻³ dm³

So 250 x 10⁻³ dm³ of solution contains .25 moles of salt

1 dm³ of solution will contain .25 / 250 x 10⁻³ mole

= 1 mole

so concentration of solution is 1 mole per dm³

a rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.