By dividing mass with volume, you will end up with density
Data that can be measured, deals with numbers and length,height,area,volume etc.
In one mole of C7H18 there are 18 moles of H (the number folowing the H)*
>> the ratio is 1:18
In 5.2 moles of C7H18 there are x moles of H
>> the ratio is 5.2:x
Cross multiply the two ratios
1x = 18×5.2
x = 93.6 moles of H
>> In 5.2 moles of C7H18 there are 93.6 moles of H
* This isnt a rule that you can always use.
However to find the mole of a certain element in a certain molucle all you have to do is count how many moles of the element are present in the molecule.
>> example1 >> H2O ;
2 H and 1 O
>> example2 >> CH3COOH ; [you add up all the moles of the same element]
(1+1) 2 C , (3+1) 4 H and (1+1) 2 O
>> example3 >> Mg(OH)2 ; [you multiply whetever is in parenthesis by the number after it 2] 1 Mg , (1×2) 2 O and (1×2) 2 H
The balanced chemical reaction is written as:
<span>2C2H2(g) + 5O2(g) → 4CO2(g) + 2H2O(g)
We are given the amount of acetylene to be used in the reaction. This will be the starting point for the calculations.
20.0g C2H2 ( 1 mol / 26.04 g) ( 5 mol O2 / 2 mol C2H2 ) ( 32 g / 1 mol ) = 61.44 g O2 is needed</span>
