Homework Help: Chemistry

Posted by Ryan on Saturday, April 21, 2007 at 10:49am.

I have no idea how to do this problems can somebody help me:
1.How many mL of and oxygen gas can be produced form the termal decmpositon of 0.340 g of hydrogen peroxide at 700°C and 755 mm Hg?
401 mL
803 mL
1200 mL
1610 mL

2.How many mL of oxygen gas at 25.0°C and 755 mm Hg can be obtained by thermal decomposition of 0.300 g of potassium chlorate?
30.1
45.1
82.3
90.0

1. Figure out how many moles of H2O2 is 0.340 g.
The reaction is
2H2O2 -> 2H2O + O2 ;
so there will be half as many moles of O2 formed as there were H2O2 to start with. Use the ideal gas law to compute the volume of that O2 at the specified temperature and pressure.

2. Do this one similarly. Start by getting the molecular weight of KClO3, convert its mass to moles, and then write down the reaction to determine how many moles of O2 are formed. Then use the ideal gas law.
We will be glad to critique your work.

a gas occupies 7.03 l at 111 kPa and 31 degrees celcious whats its volume at stp?

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