A gas is found to occupy a volume of 38.2 mL at 25.0ºC and an unknown
pressure. If this same gas occupies 37.5 mL at STP, determine what its unknown original pressure was in mm Hg.

836 mmHg

Explanation:

Given data:

Initial volume = 38.2 mL

Initial temperature = 25°C (25+273=298 k)

Final volume = 37.5 mL

Final temperature = standard = 273 K

Final pressure = standard = 1 atm

Initial pressure = ?

Solution:

Formula:  

P₁V₁/T₁ = P₂V₂/T₂  

P₁ = Initial pressure

V₁ = Initial volume

T₁ = Initial temperature

P₂ = Final pressure

V₂ = Final volume

T₂ = Final temperature

Solution:

P₁ = P₂V₂T₁ /T₂  V₁

P₁ =  1 atm × 37.5 mL × 298 K / 273 K × 38.2 mL

P₁ =  11175 atm / 10428.6

P₁ = 1.1 atm

atm to mmHg

1.1 atm × 760 mmHg / 1 atm

836 mmHg

a. the law of proportion states the combination of 2 atoms in a specific ratio to produce multiple compounds such as the given statement of question ‘1st compound contains 88.8 % cu ’ indicates 88.8 g of cu is present along with 11.2 g oxygen in 100 g of compound whereas the statement ‘2st compound contains 79.9 % cu ’ indicates 79.9 g of cu is present along with 20.1 g oxygen in 100 g of compound

1st compound contains 88.8 g cu

for cu

m = 63 g /mol

atomic % = 88.8 /63 = 1.42

for o

m = 16 g /mol

atomic % = 11.2 /16 = 0.7

b. the emperical formula of 1st compound is

cu1.4o0.7

cu2o