Molar mass and moles
The mass in grams of one mole of a substance?
Molar mass
3.18 x 105 =?
7.94 x 10-3 =?
318,000
0.00794
The measured/actual yield will always be smaller or bigger?
Smaller
How many atoms are in C6H12O6
24 atoms
C3H8 + 5O2 -> 3CO2 + 4H2O
Mole ratio of O2 and H2O
5/4
Which contains more atoms: 1 mol C3H8, 1 mol H2SO4, 1 mol NaCl
C3H8
The substance that runs out first in a reaction?
Limiting reagent
2Ga + 3Br2 -> 2GaBr3
How many grams of GaBr3 are produced when 113 grams of Br2 are reacted with an excess of Ga? Report your answer to the nearest whole number.
Ga: 69.72 g/mol
Br2: 159.80 g/mol
GaBr3: 309.42 g/mol
1. 113/159.80 = 0.7071 mol Br2
2. 0.7071*2/3 = 0.4714 mol GaBr3
3. 0.4714 * 309.42 = 146 g GaBr3
Molar mass of H2O?
18g
List all steps and names.
1. gram->mol
2. mol->mol
3. mol->gram
Measure of a chemical reaction's efficiency?
Percent yield
When 84.8 grams of iron(III) oxide reacts with an excess of carbon monoxide, 54.3 grams of iron are produced.
Fe2O3 + 3CO -> 2Fe + 3CO2
What is the percent yield of this reaction?
84.8 g / 159.69 g = 0.5310 mol Fe2O3
0.5310 mol Fe2O3 x 2 mol Fe = 1.062 mol Fe
1.062 mol Fe x 55.845 g Fe = 59.3 g Fe
54.3 / 59.3 x 100% = 91.6%
How many atoms in a mole?
6.022 x 1023
5C + 2SO2 -> CS2 + 4CO
How many moles SO2 are required to make 118 mol CS2?
236 mol SO2
How to calculate the percent yield?
actual(measured)/theoretical x 100%
A 2.80 g sample of Al reacts with a 4.15 g sample of Cl2 according to the equation shown below.
2Al(s) + 3Cl2(g) -> 2AlCl3(s)
What is the theoretical yield of AlCl3 in this reaction?
- 2.80 g / 26.98 g = 0.104 mol Al
- 4.15 g / 70.90 g = 0.0585 mol Cl2
- 0.104 mol Al x 2 mol AlCl3 / 2 mol Al = 0.104 mol AlCl3
- 0.0585 mol Cl2 x 2 mol AlCl3 / 3 mol Cl2 = 0.039 mol AlCl3
- 0.039 mol x 133.33 g = 5.20 g AlCl3
What is the mass of 2.5 moles of O2?
2.5 x 32 = 80g
2Mg+ O2 -> 2MgO
How many grams of MgO are produced when 2.37 grams of Mg are reacted with an excess of O2? Report your answer to two decimal places.
2.37 g / 24.305 g = 0.0975 mol Mg
0.0975 mol Mg x 2 mol MgO / 1 mol Mg = 0.0975 mol MgO
0.0975 mol x 40. 3044 g = 3.93 g MgO
Heating an ore of antimony (Sb2S3) in the presence of iron gives the element antimony and iron(II) sulfide.
Sb2S3+ 3Fe -> 2Sb + 3FeS
When 15.0 g Sb2S3 reacts with an excess of Fe, 9.84 g Sb is produced. What is the percent yield of this reaction?
15.0 g / 339.715 g = 0.04415 mol Sb2S3
0.04415 mol Sb2S3 x 2 mol Sb = 0.0883 mol Sb
0.0883 mol Sb x 121.76 g = 10.75 g Sb
9.84 / 10.75 x 100% = 91.5%
A tin crocodile is composed of 6.85 x 1024 atoms of tin. What is the mass of the tin crocodile in grams? Report your answer to the nearest whole number.
1. 6.85 x 1024 / 6.022 x 1023 = 11.375 mol
2. 11.375 x 118.71= 1350 g