White Board 1
1) Find the empirical formulas for the following five substances, where the percentage composition is given: a.
b.
68.8% Carbon,4.95% Hydrogen and 26.2% Oxygen
9.93% Carbon, 56% Chlorine, and 31.4% fluorine
C
7
H
6
CCl
2
F
O
2
2 c.
d.
e.
85% silver and 15% fluorine by mass
40% calcium, 12% carbon, and 48% oxygen by mass
AgF
CaCO
3
50% Magnesium, 24% carbon, 16% oxygen, and 10% hydrogen. Mg
2
C
2
H
10
O
White Board 2
1) A 2.65 gram sample of salmon-colored powder contains 0.70 grams of chromium, 0.65 grams of sulfur, and 1.30 grams of oxygen. The molar mass (molecular weight) is 392.2. What are the empirical and molecular formulas of the compound?
Empirical=Cr
2
S
3
O
12
same as molecular formula
2) A compound is found to contain 32.4% carbon, 3.6 % hydrogen, and 64.0 % oxygen. The experimental molar mass is 224.0. What is the molecular formula?
Empirical=C
6
H
8
O
9
same as molecular formula
3) Determine the empirical formula for an unknown compound composed of 38.4 % potassium,
36.3 % oxygen, 23.7 % carbon, and 1.66 % hydrogen. If the molecular weight of the compound is determined to be 306.3, what is the molecular formula?
Empirical=K
3
C
6
H
5
O
7
same as molecular formula
4) You find 7.36 g of a compound has decomposed to give 6.93 g of oxygen. The rest of the compound is hydrogen. The molecular mass of compound is 34.0 g/mole. What is the molecular formula?
Empirical=HO Molecular=H
2
O
2
1) A 2.00 g sample of ammonia is mixed with 4.00 g of oxygen. Which is the limiting reactant and how much excess reactant remains after the reaction has stopped?
Balance the reaction of gaseous ammonia plus oxygen gas reacts to form nitrogen monoxide and water:
4 NH
3
+ 5 O
2
White Board 3
 4 NO + 6 H
2
O 0.297 g excess NH
3
This is ground control to Major Tom
1) In manned space vehicles, carbon dioxide buffers use lithium peroxide (Li
2
O
2
=45.88g/mol) . It reacts with waste carbon dioxide in the air to produce lithium carbonate (73.89g/mol) and oxygen gas. There are 946.2 g of carbon dioxide present and the buffer has 925.8 g of lithium peroxide: a) Balance the reaction:
2 Li
2
O
2
+ 2 CO
2
→ 2 Li
2
CO
3
+ O
2 b) Determine the limiting reagent, show work to justify : Li
2
O
2 c) Determine the number of grams of oxygen gas produced: 322.9gO
2 d) Determine the number of grams of excess reagent left over in the reaction:
946.2 - 888.1 = 58.1 g CO
2

White Board 4
Integrated:
1) A compound is found to contain 92.24% carbon, 7.757 % hydrogen. This hydrocarbon has a molar mass of ~ 78 g. If 25.5 g of this compound completely combusts with 83.4 g of oxygen, then determine how many liters of carbon dioxide and how many mL of liquid water are produced.
2 C
6
H
6
+ 15 O
2
 12 CO
2
+ 6 H
2
O 17.6 mL H
2
O 43.9 L CO
2 or
86.3 g CO
2
White Board 5
Stop playing with fire, you pyro!
1) 4.43g of potassium is burned to form a product with a mass of 5.34g. What is the empirical formula of this oxide?
K
2
O
2) 250.0 g of potassium metal reacts with 250.0 g of water to produce potassium hydroxide and hydrogen gas. a.
Write the balance equation: 2 K + 2 H
2
O → 2 KOH + H
2 a.
Identify the limiting reagent (show work to justify): K b.
Determine the mass of potassium hydroxide produced.
358.8g KOH c.
Determine the mass of excess reagent left over.
134.8 g H
2
O
3) With a slight amount of activation energy (a spark), butane ( C
4 oxygen.
H
10
)=58.14g/mol will combust with a) Determine the products and write & balance the equation:
2 C
4
H
10
+ 13 O
2
→ 8 CO
2
+ 10 H
2
O b) How man grams of each product will be produced if 2.60 pounds of butane and 4.42 kg of oxygen gas are ignited? (1lb=453.6 g) Also, determine the mass of excess reagent left over.
1830 g H
2
O
3570 g CO
2
2.00x10
2 gO
2
excess
White Board 6
Don’t be so diluted!
1) Calculate the molarity of a diluted solution when 35.0 mL of a 4.00 M NaCl solution is diluted to 0.250 L.
1.79M
2) A 500. ml solution is made with 366.0 g of AuCl
3
=303.32g/mol. What is the Molarity of the solution?
2.41 M
3) How many grams of Fe(C volume of 2.0 L?
2
H
3
O
2
)
2
= 173.95g/mol would be required to produce a 3.8 M solution with a
1300 g of Fe(C
2
H
3
O
2
)
2
4) What is the molarity of a 35.009 g of sodium phosphate 147.94g/mol dissolved in 0.078 L? 3.0 M
5) Calculate the molarity when 550.0 grams of Al(NO
3
)
3
= 213.01g/mol is dissolved in 1200.0 mL of solution.
2.152 M
6) What volume (in mL) of 4.50 M HCl will be needed to make 3.00 L of a 0.020 M solution? 13.3 mL