Calculations
Percent composition: mass of element X 100
mass of the compound
1. ZnBr2
2. Iron (III) nitride
3. Tetraphosphorus decaoxide
4. What is the percent nitrogen in ammonium nitrate?
Percent error: |experimental – accepted| X 100
Accepted
1. The density of water at 4oC is known to be 1.00 g/mL. You experimentally found the density of water to be 1.075 g/mL. What is your percent error?
2. An object has a mass of 35.0 grams. On your balance, it weighs 34.85 grams. What is the percent error of your balance?
3. You missed ten points on your lab report. The teacher told you that you were 30.8% too low in the boiling point you recorded (50o C). What is the correct boiling point of the liquid you were working with in lab?
Percent yield: Actual Yield X 100
Theoretical Yield
1. H2SO4 + Ba(OH)2 ------> BaSO4 + H2O
If 98.0 g of H2SO4 is reacted with excess Ba(OH)2, determine the percent yield of BaSO4 if you isolate 213.7 g of BaSO4.
2. My theoretical yield of beryllium chloride was 10.7 grams. If my actual yield was 4.5g, what was my percent yield?
3. H3PO4 + 3 KOH ------> K3PO4 + 3 H2O
If 49.0 g of H3PO4 is reacted with excess KOH, determine the percent yield of K3PO4 if you isolate 49.0 g of K3PO4.
Molarity: (M) mol/L
1. What is the molarity of a 25.5 L solution containing 34 moles of solute?
2. 15.8 g of KCl is dissolved in 225 mL of water. Calculate the molarity.
3. What is the molality of a solution containing 22.5 grams of Na2O in 450 grams of water?
4. Calculate the volume of 0.30 M KCl solution that contains 6.00 g of KCl.
Empirical formula:
1. 43.7% phosphorus, 56.3% oxygen
2. 56.8% carbon, 5.3% hydrogen, 37.9% oxygen
3. What is the molecular formula for a compound composed of 25.9% nitrogen and 74.1% oxygen that has a molecular mass of 324 amu?
Molecular formula:
1. What is the molecular formula of a compound that has an empirical formula of CH2 with a molar mass of 56g?
2. What is the molecular formula for a compound that has an empirical formula of CH2O and has a molar mass of 90g?
3. A compound has a molecular mass of 220g and an empirical formula of P2O3. What is its molecular formula?
Limiting reagent:
1. For the reaction: Na2O + H2O à NaOH
What would be the limiting reagent if 100 g each of Na2O and H2O were allowed to react?
What weight of NaOH could be made from 12.4 g of Na2O and 42.1 g of H2O?
2. A sample of 23.4 grams of sodium hydroxide is mixed with 18.7 grams of lithium sulfide, producing lithium hydroxide and sodium sulfide. What is the limiting reagent?
3. 3Mg + 2H3PO4 à Mg3(PO4)2 + 3H2
When 5.4g of magnesium is treated with 8.3g of phosphoric acid, the products are magnesium phosphate and hydrogen gas. What is the limiting reagent? (Mg-24.31, H3PO4-98.00, Mg3(PO4)2-262.86, H2-2.02)