Question

HELP . How many liters of oxygen gas can react with 84.0 grams of lithium metal at standard temperature and pressure? Show all of the work used to find your answer.

4Li + O2 yields 2Li2O

Answer 1

to find the liters of O2 you will need the moles. So to find the moles you will use the lithium and find the mol to mol ratio

Answer 2

to find moles of lithium divide 84/7 ( molar mass of lithium)
you get 12 moles of Li

Answer 3

you have the balanced equation, for every 4 moles of Li, you need 1 mol of O2

so 12x (1/4)=3
so you have 3 mole of O2

Answer 4

to find the liters of o2 gas, you use the ideal gas law
PV=nRT.
p=Pressure(atm)
v=volume (L)
n=mole of gas
R=.0821 L*atm/mol*K (constant)
T= temp. (kelvin)

Answer 5

since the question says, standard temperature and pressure, so that means 1 atm(pressure) and 273 K(temp.)

so now you have everything, just plug and chug,
P=1 atm
V=? L
n=3 mol
R=.0821
T=273 K

(1)(V)=(3)(.0821)(273)

V= 67.24 Liters of O2