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Old Oct 25th 2015, 05:40 PM   #1
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Talking Help with a few practice problem for Chem 107 please!

1) A 2.5L mixture contains 3 gases. N2, He, and Ne at partial pressures of .32 atm of N2, .15 atm He, and ,.42 atm Ne. Calculate the total pressure.

2) A mixture of He and Ne gases are collected over water at 28.0C and 745 mmHG. If the partial pressure of He is 368 mmHg, what is the partial pressure of Ne? (Vapor pressure of water at 28C= 28.3mm Hg)

3) A 0.050g sample of CO2 is placed in a 4.6L vessel at 30C. Calculate the pressure inside. (I worked this one out but kept getting the wrong answer)

4) A sample of zinc metal is allowed to react completely with excess of hydrochloric acid:
Zn(s) + 2HCL (aq) --> 2nCl2(aq) + H2(g)

The hydrogen gas produced is collected over water at 25.0 C. The volume of the gas is 7.80L, and the pressute is .980 atm. Calculate the amount of zinc in grams consumed in the reaction. (Vapor pressure of water at 25= 23.8 mmHg)

Last edited by Acrainae; Oct 25th 2015 at 05:44 PM.
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Old Oct 25th 2015, 07:22 PM   #2
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A)Total pressure is the pressure exerted by all gases in the container.

P (total) = sum of all three partial pressures
B) P(Total)= P(He)+P(Ne)+P(H2O)-----(1)
In the question
P(Total),P(He) and P(H2O) is given ...just use the equation (1)
here P=nRT/V
n= mass of CO2/Molar mass
T(use in K) and V are given ...R is a constant ...its value you can get from the book
match the units of R with the units of P,V.T and mole ...you are good to go ...
D) Get the pressure of the dry H2 formed in the reaction
PH2= P(total)-P(H2O)
Then use ideal gas law to get the moles of H2
and now you have the balanced equation so convert moles of H2---> to moles of Zn....> g of Zn
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chem 107, general chemistry, ideal gas law, partial pressure

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