Chem/Math help urgent please.?

Posted on 2015-10-29 07:30:00 in Chemistry by MACK

I have a series of questions I am not understanding. between work and school I cant get into the professor, so if someone could explain how to accomplish these problems that would be grand. Thank you

A gas mixture contains the following gases at the indicated partial pressures: N2, 335 torr ; O2, 124 torr ; and He, 217 torr. What mass of each gas is present in a 3.00 L sample of this mixture at 25.0 ?C?

The air in a bicycle tire is bubbled through water and collected at 25?CIf the total volume of gas collected is 5.65 L at a temperature of 25?C and a pressure of 732 torr , how many moles of gas were in the bicycle tire? ( i have multiple questions involving the added air vapor vairiable and im just not understanding how to get the air vapor amount and how to utilize it.

The zinc within a copper-plated penny dissolves in hydrochloric acid if the copper coating is filed down in several spots (so that the hydrochloric acid can reach the zinc). The reaction between the acid and the zinc is

2H+(aq)+Zn(s)?H2(g)+Zn2+(aq).

When the zinc in a certain penny dissolves, the total volume of gas collected over water at 25 ?C is 0.953 L at a total pressure of 747 mmHg. (Vapor pressure of water is 23.78 mmHg at 25 ?C.) What mass of hydrogen gas is collected?

Consider the following chemical reaction:
2H2O(l)?2H2(g)+O2(g)
What mass of H2O is required to form 1.4 L of O2 at a temperature of 335 K and a pressure of 0.903 atm ?

one question says to assume STP conditions... what is STP

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