The molar masses of four unknown gases are shown in the table. Molar Mass of Unknown Gases
Gas Molar Mass
A 44 g/mol
B 20 g/mol
C 30 g/mol
D 32 g/mol
Which gas is likely to have the lowest rate of diffusion?
a. Gas A
b. Gas B
c. Gas C
d. Gas D

a. Gas A has the lowest rate of diffusion

Given

The molar masses

Required

the lowest rate of diffusion

Solution

Graham's law: the rate of effusion of a gas is inversely proportional to the square root of its molar masses or  

the effusion rates of two gases = the square root of the inverse of their molar masses:  

So  :

The greater the molar mass, the smaller the rate

So gas A has the lowest rate

the only liquid elements at standard temperature and pressure are bromine (br) and mercury (hg). although, elements caesium (cs), rubidium (rb), francium (fr) and gallium (ga) become liquid at or just above room temperature.

explanation:

- lead + phosphoric acid = hydrogen + lead(ii) phosphate