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Unit 9: Stoichiometry
Differentiate between the significance of the coefficients in a balanced chemical equation and the significance of the subscripts in a chemical formula. ·
Coefficients show the correct proportions of atoms and molecules in a chemical reaction. They are normal sized numbers placed at the beginning of the chemical formulas in a chemical reaction during the process of balancing. They tell how many of an entire chemical formula is in a reaction. ·
Subscripts show the correct proportions of atoms/ions in a chemical formula. They are the small numbers within the chemical formula. They tell how many individual atoms/ions are present. 2.
State the Law of Conservation of Mass and explain its relationship to stoichiometry. The Law of Conservation of Mass states that “Matter can neither be created nor destroyed during a chemical reaction.” This law is dictates the necessity for balancing a chemical equation with coefficients; if we didn’t balance equations, we would be created and/or destroying chemicals. 3.
One disadvantage of burning propane (C3H8) is that carbon dioxide is one of the products. The released CO2 increases the growing concentration of CO2 in the atmosphere. How many moles of carbon dioxide are produced when 10.0 moles of propane are burned in excess oxygen on a gas grill? C3H8 + 5O2 → 3CO2 + 4H2O
Water decomposes to produce hydrogen gas and oxygen gas. How many grams of water would be required to
produce 10.0 moles of hydrogen gas?
2H2O → 2H2 + O2
MMH2O = 18.015 g/mol
If 25.0 grams of carbon dioxide are used in photosynthesis how many moles of glucose (C6H12O6) could be
Produced according to the following equation: 6CO2 + 6H2O C6H12O6 + 6O2 MMCO2 = 44.009 g/mol
One series of reactions that inflates air bags in automobiles is the decomposition of sodium azide (NaN3). Determine the amount of N2 produced if 100.0 g of NaN3 is decomposed using the following unbalanced equation: 2NaN3 2Na + 3N2
MMNaN3 = 65.011 g/mol
MMN2 = 28.014 g/mol
limiting reactant problem:
Nitrogen gas reacts with hydrogen gas to produce ammonia: ___N2 + ___H2 ___NH3 *not balanced If 100.0 g of nitrogen gas reacts with 20.0 g of hydrogen gas what mass of ammonia will be produced?
N2 + 3H2 2NH3
MMN2 = 28.014 g/mol
MMH2 = 2.016 g/mol
MMNH3 = 17.031 g/mol
LIMITING REACTANT = H2 because after 113 g NH3 is produced, H2 runs out EXCESS REACTANT = N2 because it could have made 122 g NH3 if H2 hadn’t run out first. THEORETICAL YIELD = 113 grams of ammonia
Mass to mass and Percent Yield problem:
Iron reacts with oxygen to form Iron (III) oxide. 4Fe + 3O2 2Fe2O3. a)
If 200.0 g of iron reacts, what is the theoretical yield of iron (III) oxide? b)
If the actual yield is 205.4 g, what is the percent yield of the reaction?
MM Fe2O3 = 159.691 g/mol
Unit 10: States of Matter
Place a check in the box if the description applies to solids, liquids and/or gases. Each characteristic may apply to 1, 2 or all 3 states: |Solids|Liquids|Gases|
Takes the shape of its container||Yes|Yes|
Fills the volume of its container|||Yes|
Particles are far apart from one another|||Yes|
Molecules are moving|Yes|Yes|Yes|
Fill in the chart below: (a thru f)
Which of the above (a thru f) are exothermic? D, E, F
Which of the above (a thru f) are endothermic? A, B, C
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