[hellomyfriends]

what weight of oxy gen obtained by the thermal decomposition of 2.45 g of potassium chlorate ? K=39 , Cl=35.5 , O= 16

2.45----------?g
2KClO3-------2KCl+3O2
2 moles--------- 3 moles
1 moles----------3/2 moles

KClO3,, 1 mole is 39 + 35.5+(3x16)=122.5g

2.45g is 2.45/122.5=1/200

How do you get that mole ratio of 1/200?
i'm using some coles notes, hte sample is suppose to be divided by the molecular gram weight to get the mole ratio. This is done for the rest of the questions in the notes. I understand this, but i do not understand why why this ratio is done.
This is probably going to be something very simple -.-.
Thank you

[sjb]

I'm not overly sure what you're asking here. You're aware that a mole is just a given number of ions, molecules or similar; just like a dozen, gross or score?

2.45 g divided by 122.5 g mol^-1 is 5 x 10^-3 mol, or 1/200...?

[hellomyfriends]

I'm not overly sure what you're asking here. You're aware that a mole is just a given number of ions, molecules or similar; just like a dozen, gross or score?

2.45 g divided by 122.5 g mol^-1 is 5 x 10^-3 mol, or 1/200...?

Thank you for answering, I am aware that a mole is a give number of parts, electrons protons and etc, adding to a total of 6.02×10^23.
What I want to know is math involved. The step by step mathematical  process of how the ratio is 1/200

122.5 g mol-1
why is there an exponent to the power of negative one
I do not get 5 x 10-3 when I divide those numbers into my calculator

[sjb]

Ahh, partly my fault, the answer to your sum is actually 1/50, or 2 x 10_-2. Where (before my mistake) did you see 1/200 ?

The exponent to the power of -1, is just another way of writing ^g/_mol - perhaps see http://en.wikipedia.org/w/index.php?title=Exponentiation&oldid=304915185 ?

[hellomyfriends]

thank you again
*gives mole snack*

That is the ratio given in the question. Here is the rest of the answer

therefore, 3/2x1/200 moles of oxygen is produced

1 mole of O2 is 32 g, 3/2x1/200 mole is 3/2 x 1/200 x 32 =0.24 g

This is how the answer is given in the book.

I thought about multiplying the 122.5 by 2 moles but 3/2 includes that ratio

[sjb]

Hmm, seems like there may be an error somewhere.

2.45 g of KClO₃ is 0.05 mol, from the reaction equation that yields 0.075 (multiplying by 1¹/₂) mol of O₂, which has mass...?

Not sure why 1/200 is mentioned, to be honest

[hellomyfriends]

ok, the book is at fault , thank you for clearing that up