chemistry

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A 2.45 gram sample of potassium chlorate is heated an the oxygen gas collected. what is the volume of the oxygen at STP.

Is the oxygen gas itself 2.45 grams or do I have to subtract something from that?

• chemistry - ,

No, the KClO3 from which the oxygen is evolved, has a mass of 2.45 g. You need to write the equation, balance it, convert 2.45 g KClO3 to mols, convert mols KClO3 to mols O2 using the coefficients in the balanced equation, then convert mols O2 to liters knowing that 22.4 L is the volume occupied by a mole of a gas at STP. USUALLY, oxygen is collected over water and that must be corrected for the vapor pressure of water; however, your problem doesn't say anything about water; therefore, I asume we don't need to worry about that.Post your work if you get stuck and we can help you through it.

• chemistry - ,

what reactants would there be besides O2?

• chemistry - ,

Heating KClO3 produces oxygen and potassium chloride.
KClO3 + heat ==> KCl + O2
The balanced equation is:
2KClO3 ==> 2KCl + 3O2.