[lokobreed]

1) Balance the equations. What  mass of KCLO3 decomposed to produce 275 ml of O2 gas at STP.
___ KCLO3 --> __ KCL + __ O2
Balancing would yield
2 KCLO3 --> 2 KCL + 3 O2
I am now confused on the following steps I should take to solve the rest of the problem.

2)Balance the following equation and calculate the volume od hydrogen gas produced from the reaction of .762 g of aluminum when completely reacted with excess hydrochloric acid. The gas was collected over water at 27 C and barometric pressure of 747.
__ Al + HCL --> __ AlCl3 + __ H2
Balancing would yield
2 Al + 6 HCL --> 2AlCl3 + 3 H2
- vapor pressure = 26.7
- pressure of dry hrdrogen = .947 atm
- Kelvin temp = 300 K
I am confused on how to setup the rest of the problem.

[rabolisk]

If the question asked, what mole of KClO₃ is decomposed to produce x mol of O₂ gas, could you do it?

[lokobreed]

i believe so but I am confused on the meaning of O2 at stp... because wouldnt I need the temperature to solve this?

[rabolisk]

STP means Standard Temperature and Pressure.

http://en.wikipedia.org/wiki/Standard_conditions_for_temperature_and_pressure

Question 2 is the same as 1 except you are explicitly given the conditions.

[lokobreed]

I am going to attempt snd solve the 2nd one first.

I would first convert how many mols are in .762 g of aluminum =  .0282 mols
looking for volume so,
V= nRT/P

V= .0282 * .082 * 300 / .947 = Volume

is this correct?

[rabolisk]

You forgot a step. You're looking for the volume of H₂, not the volume of Al.

[lokobreed]

take the .0282 mols of al x 3 mols of H2 / 2 mols of Al = .0424 mols oh H2

Thus V= .0424 mols of H2 * .082 * 300 / .947 = Volume

[rabolisk]

Looks good.