3. A volume of 546 mL of hydrogen is collected over water at 30 degrees * C when the atmospheric pressure is 100.45 kPa. How many moles of hydrogen are present ?

Number of moles of hydrogen are 0.022 mol.

Explanation:

Given data:

Volume of hydrogen = 546 mL

Temperature = 30°C

Pressure = 100.45 kpa

Number of moles of hydrogen = ?

Solution:

According to ideal gas equation,

PV = nRT

P = pressure

V = volume

n = number of moles

R = ideal gas constant

T = temperature

First of all we will convert the units,

Temperature = 30 + 273 = 303 K

Pressure = 100.45 /101 = 0.99 atm

Volume of hydrogen = 546 mL× 1L /1000 mL =0.546 L

Now we will put the values in formula,

PV = nRT

n = PV/RT

n = 0.99 atm × 0.546 L /0.0821 atm.L/mol.K × 303 K

n = 0.541 atm. L / 24.876 atm.L / mol

n = 0.022 mol

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.