Chemistry Chap 10
how do you solve percent composition? (must add up to 100%)
mass of element/mass of compound x 100
percent composition
mass of element/mass of compound x 100
How does the mole relate to the dozen?
The mole is a unit for counting 6.02 1023 representative particles. The dozen is used to count 12 items. Each one-mole quantity has 6.02 1023 particles (atoms), but they will have different masses.
Find the percent composition of a compound formed when 29.0 Ag combines with 4.30g S
29.0 + 4.30 = 33.3g 29./33.3 4.30/33.3 87% S 12S
What is the molar mass of caSO4?
40.07(molar mass of CA) + 32.06 (S)+ (O)16(4) = 136.13
Avogadro's number
6.02 x 10^23 (particles in a mole)
Empirical formula example
67.6% HG, 10.8% S, 21.6% O 67.6g times 1 mole divided by 200.6(HG) = .33 10.8 times 1 mole divided by 32(S)= .33 21.6 times 1 mole divided by 16(O)= 1.35 .33/.33 .33/.33 1.35/33 Hg1, S1, and O4
What is the mass, in grams, of 945 mol of aluminum oxide (AI2O3)
9.45x101.961 = 963.53 grams. (Final) 26.98(2) + 16(3) = 101.961
How do you solve for empirical formula?
94.1% O, 5.9%O 94.1 x 1 mole divided by 16(O) = 5.88
AT STP, how many moles are in 1.00 x 10^3 L C2 H6
(1.00 x 10^3) x 1 mole divided by 22.4 = 44.64
how do you calculate the molar mass of a compound?
1) find number of grams of each element in one mole of a compound 2) Then add the masses of elements in compound
How many moles of Magnesium (Mg) is 1.25 x 10^23 atoms of Mg
1.25 x 10^23 x 1 mole divided by 6.02 x 10^23
How many atoms are in 2.12 mol of propane (C3,H8)
2.12mol x 6.02 x 10^23 divided by 1=
molar volume
22.4 L, or the volume occupied by one mole of a gas at STP
When would we use molar volume in a problem?
When you are given a mass or gram option
empirical formula
a chemical formula showing the ratio of elements in a compound rather than the total number of atoms
When would we use molar mass in a problem?
calculate the mass of a compound and to convert moles to grams
STP (standard temperature and pressure)
conditions of 0.00°C and 1 atm pressure
What does the mole allow chemists to do?
count the number of representative particles in a substance
mole
specified number of particles
Avogadro hypothesis
states that equal volumes of gases at the same temperature and pressure contain equal numbers of particles
molar mass
the mass of one mole of a pure substance
Representative particle
the species present in a substance, usually atoms, molecules, or formula units
