Math in chemistry Flashcards
(13 cards)
How to do write a valid measurement using sigfigs
there should be one estimated digit at the end
Are leading zeros sigfigs
0.0049
No They are not
They are the zeros that come before the digits.
That only has 2 sigfigs
0.00405 how many sigfigs
3
Leading zeros are not significant but the sandwiched zeros are.
Are trailing zeros sigfigs
25,000
25000.0
Hard to tell, The num of sigfigs in 25,000 is at least 2 but there could be more
Use scientific notation
unless it is after a decimal point . 25000.0 has 6 sigfigs
sigfigs from additions and subtraction vs multi and divide
+- - answer has same amt of decimals as the measurement with the fewest decimals
*/ - round or add zeros to have the same number of significant digits as the measurement with the fewest significant figures
avogadros constant or the number of a mole is
6.02 x 10^23
How do you calculate the amount of particles of a substance
get the amt of moles then multiply by 6.02 x 10^23
What is percentage comp
How do you calculate percentage composition
the percentage, by mass, of each element in the compound
% composition = mass of element in compound / total mass of compound *100%
it will give you the empirical formula
What is the law of definite preportions
The elements in a chemical compound are always present in the same proportions by mass”
Molecular formula vs empirical formula
The molecular formula is the actual formula of the compound
The empirical formula is the formula of the compound that has the lowest numbers of the same ratio
ex C6H6 and CH
Rhyme to convert to empirical
!Percent to Mass
!Mass to Mole
!Divide by Small
!Multiply ’till Whole”
What is theoretical yield vs actual yield
Theoretical - the amt expected based off of the stoichiometry
actual - the amt that was obtained in experiment
How do you calculate percentage yield of an experiment
P Yield = actual/ theoretical * 100%
