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What is the Molar Mass of H2O? (Include Units)
18.016 g/mol
What is Avogadro's Number? (Include Units)
6.022 x 10^23 atoms/mole
What is the unit of Molar Mass?
g/mol
How many Phosphorus's are in Phosphate?
1 Phosphorus - PO4
How many Chlorines are in Magnesium Chloride?
2 Chlorines - MgCl2
How many moles are in 2.6 grams of Helium (He)? Include all work and units
2.6 / 4.003 = 0.60 moles He
How many moles are in 3.2 x 1023 atoms of silver? (include all work and units)
(3.2 x 1023 atoms Ag) / (6.022 x 1023 atoms Ag) = 0.50 moles of Ag
How many grams are in 0.41 moles of Oxygen (O)? (Include all work and units)
0.41 moles) * 16 grams O = 6.6 grams O
How many atoms are in 0.045 moles of Zinc? (include all work and units)
0.045 moles Zn * (6.022 * 1023 atoms Zn) = 2.7 * 1022 atoms Zn
How many grams are in 2.3 moles of Sodium (Na)? (include all work and unit)
2.3 moles Na * 22.99 grams Na = 52.9 (53 sig fig) grams of Na
What is the Molar Mass of NaCl? (Show all work and units)
22.99 + 35.45 = 58.4 g/mol NaCl
What is the percent composition of Magnesium in Magnesium Oxide (MgO)? (Show all work and units)
MgO = 24.30 + 16.00 = 40.30
% Mg = (24.30 / 40.30) * 100 = 60.30 % Mg
What is the Molar Mass of Li2(CO3)? (Show all work and units)
2(Li) + 1(C) + 3(O)
2(6.94) + (12.01) + 3(16.00) = 73.9 g/mol
What is the Percent Yield if in the lab Marissa and Daniel got 3.4 g. But when Isa and Femiel did the math - they theoretically should have produced 4.1 g. What is the groups percent Yield? (Show all work and include units)
(3.4/4.1) * 100 = 82.90 %
What is the Molar Mass of Calcium Bromide? (Show all work and Units)
1(Ca) + 2(Br)
40.08 + 2(79.90)
199.9 g/mol
A sample has 75.74% arsenic and 24.26% oxygen, what is the empirical formula? (assume 100g - show all work and units)
As (75.74/74.92) = 1.0
O (24.26/16) = 1.5
As = 1.0/1.0 = 1 (*2) = 2
O = 1.5/1.0 = 1.5 (*2) = 3
As2O3
What is the Molar mass of Potassium Phosphate? (include all work and units)
K3(PO4) = 3(K) + 1(P) + 4(O)
3(39.10) + (30.97) + 4(16) = 212.27 g/mol
How many grams are in 0.0065 moles of Lithium Sulfide? (Show all work and units AND SIG FIGS)
Li2S = 6.94 + 2(32.06) = 71.06 g/mol
0.0065 moles Li2S * 71.06 g/mol Li2S = 0.46189 grams
0.46 grams Li2S
What is the percent composition of all elements in table salt (sodium chloride)? (show all work and units)
NaCl = 22.99 + 35.45 = 58.44
%Na = (22.99/58.44) * 100 = 39.34 % Na
%Cl = 100% - 39.34 = 60.66 % Cl
How many Moles are in 78.3 grams of Potassium Bromide? (Include all work and units AND SIG FIGS)
KBr = 39.10 + 79.90 = 119 g/mol KBr
78.3 grams KBr / 119 g/mol KBr = 0.65798 moles
0.658 moles KBr
Use the Balanced Equation:
2Al + 6HCl --> 2AlCl3 + 3H2
If you start with 0.555 mol Al and 0.411 mole HCl, what is the Limiting Reactant? (Show all work and units)
Reactants --> AlCl3 (mole ratio)
Al: 0.555 mol Al * (2 moles AlCl3/2 moles Al) = 0.555 moles AlCl3
HCl: 0.411 mol HCl * (2 moles AlCl3/6 moles HCl) = 0.137 moles AlCl3
HCl is limiting Reactant
Use the balanced equation:
3Si + 2N2 --> Si3N4
If you start with 1.50 grams of N2 and 0.023 moles of Si3N4 is produced. How much excess of N2 is left over?
0.023 moles Si3N4 * (mole ratio) = 0.046 moles N2
0.046 moles N2 * MMN2 = 1.28892 grams N2
starting - used
1.5 g - 1.28892 g = 0.211 grams N2
Find the Empirical AND Molecular Formula:
A compound is 23.3 g magnesium, 30.7 g sulfur, and 46.0 g oxygen. What is the Empirical Formula? If the compound weighs 313.08 grams, what is the molecular formula? (Show all work and units)
Mg: 23.3/24.30 = 0.9588 divide by lowest = 1
S: 30.7/32.06 = 0.9576 divide by lowest = 1
O: 46/16 = 2.875 divide by lowest = 3
Empirical = MgSO3 = 24.3 + 32.06 + 3(16) = 104.36
Molecular = (313.08/104.36) = 3 MULTIPLY
Mg3S3O9
Balance the Equation then determine how many grams of O2 there are if Asher brings 28.1 grams of water to class:
H2 + O2 --> H2O
(Show all work, Units and SIG FIGS)
2,1,2
Grams H2O --> Grams O2
28.1 grams H2O / MMh2o = 1.5597 mol H2O
1.5597 mol H2O * (mole ratio) = 0.77986 mole O2
0.77986 mole O2 * MMO2 = 24.955 g O2
25.0 g O2
How many atoms are in 6.1 * 103 grams of Calcium Chloride? (Show all work, units, AND SIG FIGS)
Grams --> Atoms
MM CaCl2 = 40.08 + 2(35.45) = 110.98 g/mol
(6.1 * 102 grams CaCl2) / MMCaCl2 = 5.496485 moles CaCl2
5.4964 moles CaCl2 * Avogadros Number = 3.30998 e24
3.3 * 1024 atoms CaCl2