Moles Flashcards
the atomic mass is essentially equal to the mass of its _______
Nucleus
Atoms can be directly measured (T/F)
False, because they are so tiny
This is the standard of which atoms are measured
C-12 (Carbon-12) measured in unified atomic mass units (u)
one u is equal to…
1/12 of a C-12 atom (1u=1.66054 x 10^-24g)
an element many have different isotopes (T/F)
True, example: hydrogen-1 (1p,1e, 0n)
hydrogen-2 (1p, 1e, 1n)
hydrogen-3 (1p,1e 2n
the isotopic abundances are
percentages in any sample of an element that contains varying percentages of each isotope
ex. Any sample of lithium will contain 92.58% of Li-7 and 7.42 Li-6
average atomic mass can be found by…
- looking at the periodic table
- calculating A.A.M (average atomic mass) by multiplying percentage with the mass of the isotope and adding it with other isotopes given.
the Mole aka.
Avogadro’s number
the mole is… (value)
6.02 x 10^23
(T/F) We cannot use atomic mass to determine molar mass
False, molar mass and atomic mass are the same except units are different.
atomic mass= # u
molar mass= # g/mole
if you have 1 mole of a substance you have…
6.02 x 10^23 particles
N=n Na
uses?
meaning of variables?
to calculate the amount of particles/atoms/molecules in any given amount of mole or vice versa.
N=# of particles/atoms/molecules
n=# of moles
Na=Avogadro’s number
“any sample of pure compunds alwats contains the same elements combined in the same proportion by mass
Joseph Proust (1754-1826)
Calculating the %by mass of each element in sugar (C 6 H 12 O 6)
- assume that we have one mole of the substance.
- Calculate molar mass of entire molecule
- Calculate mass of 1 mole of the molecule
- For each element find the mass by multiplying the number of moles (ex. Carbon has 6 moles of atoms) by molar mass of element then divide by total molar mass to get percentage.
simplest “reduced” formula
Empirical Formula
