defffusing rate
Posted: Wed Oct 22, 2008 8:41 pm
Newly minted pennies are made of zinc with a thin copper shell. If the copper coating in nicked, hydrochloric acid can attack the zinc, leaving the copper intact. The hydrochloric acid and the zinc react according to the following equation :
2HCl + Zn ---> ZnCl2 + H2
the hydrogen gas generated from the reaction of HCl with a 2.543 g penny was collected over water at 24.0 C degree when the total pressure in the collection flask was adjusted to barometric pressure 738.7 torr, the volume of the hydrogen gas was deteremined to be 982 mL. The vapor pressure of the water at 24.0 degree C is 22.4 torr Find the mass of zinc in this penny
this has to do with PV=nRT and stoicheometry
we know V is .982 L
P is 738.7 - 22.4 from water 715.3 torr/ 760 = atm
and T is 24 + 273 = 297 K
i don't know what to do since the question is confusing to me
it asks mass of zinc in this penny
i did PV = n RT to find moles of hydrogen
then convert to mole of Zn using mole ratio
then times the mole of Zn by molar mass and obtained 2.47975 g Zn
is this correct???? i did use the info they gave of the penny weighin 2.543g
second question
An auditorium contains 50 rows of seats numbered 1 through 50 from front to back. If laughing gas, N2O, is released from the front of the room at the same time HCN is relesed from the back of the room, in which row counting from the front will people begin to die laughing?
we have graham's law of rateA/rateB = sqrt(Molar mass b / molar mass a)
so i have
rate N2O / rate HCN = sqrt (27.028/44.02)
rate N2O / rate HCN = .78577
meaning rate of N2O is smaller than rate of HCN
thus HCN is defussing at a faster rate than N2O
if N2O was released from the front row of auditorium
then the ppl dying from laughter has to be between row 1 and 25
but i don't know how to figure out the exact row
please help
2HCl + Zn ---> ZnCl2 + H2
the hydrogen gas generated from the reaction of HCl with a 2.543 g penny was collected over water at 24.0 C degree when the total pressure in the collection flask was adjusted to barometric pressure 738.7 torr, the volume of the hydrogen gas was deteremined to be 982 mL. The vapor pressure of the water at 24.0 degree C is 22.4 torr Find the mass of zinc in this penny
this has to do with PV=nRT and stoicheometry
we know V is .982 L
P is 738.7 - 22.4 from water 715.3 torr/ 760 = atm
and T is 24 + 273 = 297 K
i don't know what to do since the question is confusing to me
it asks mass of zinc in this penny
i did PV = n RT to find moles of hydrogen
then convert to mole of Zn using mole ratio
then times the mole of Zn by molar mass and obtained 2.47975 g Zn
is this correct???? i did use the info they gave of the penny weighin 2.543g
second question
An auditorium contains 50 rows of seats numbered 1 through 50 from front to back. If laughing gas, N2O, is released from the front of the room at the same time HCN is relesed from the back of the room, in which row counting from the front will people begin to die laughing?
we have graham's law of rateA/rateB = sqrt(Molar mass b / molar mass a)
so i have
rate N2O / rate HCN = sqrt (27.028/44.02)
rate N2O / rate HCN = .78577
meaning rate of N2O is smaller than rate of HCN
thus HCN is defussing at a faster rate than N2O
if N2O was released from the front row of auditorium
then the ppl dying from laughter has to be between row 1 and 25
but i don't know how to figure out the exact row
please help