harrisxml Posted January 11, 2004 Share Posted January 11, 2004 I am doing stoicheometry which deals with mole ratios of compounds in a reaction. Anyways, if the ratio is 2:7 than how would I go about getting from the number with the 2 as its ratio to the number with 7 as its ratio. example: 4.50g= the 2 x= the 7 what do I do to get to the 7 ratio. Link to comment Share on other sites More sharing options...
Jason the Eighty Eighth Posted January 11, 2004 Share Posted January 11, 2004 could you rephrase your post? it's really hard to understand. Link to comment Share on other sites More sharing options...
m0fo Posted January 11, 2004 Share Posted January 11, 2004 to find out what x is, divide 4.50g by 2, then multiply by 7 Link to comment Share on other sites More sharing options...
harrisxml Posted January 11, 2004 Author Share Posted January 11, 2004 I have 4.5 grams of one substance. I have x grams of another substance. The ratio between them is 2:7. How do I find X? Link to comment Share on other sites More sharing options...
SMeK Veteran Posted January 11, 2004 Veteran Share Posted January 11, 2004 if you have a value of the 2 version you do 7 divided by 2 to work out the difference thing then multiply your value of 2 by the value you just worked out so (RatioA/RatioB)*ValueOfA = answer Link to comment Share on other sites More sharing options...
harrisxml Posted January 11, 2004 Author Share Posted January 11, 2004 Thanks very much guys. I got it now. Link to comment Share on other sites More sharing options...
I8PP Posted January 11, 2004 Share Posted January 11, 2004 First, you must change whatever the 4.50g substance (your example) into moles. If the reaction was 2A -> 7B and hypothetically the moles of A was 1.00 moles, then B would be half of A times 7. Once you have the moles of B, work backwards using the formula: moles = (mass / molecular mass) to find the mass of substance B, assuming you know what the molecular mass of the substance is... Edit: Bah, i took too long ;). Yippie, 600th post :happy: Link to comment Share on other sites More sharing options...
Jason the Eighty Eighth Posted January 11, 2004 Share Posted January 11, 2004 i got 15.75g. Link to comment Share on other sites More sharing options...
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