Unit 4 Chemical Reactions and Stoichiometry Review
Unit 4 Chemical Reactions and Stoichiometry Review
Chemical Reactions
Plants combine carbon dioxide, water, and sunlight in a process called ______to produce glucose and oxygen gas.
6 CO2 (g) + 6 H2O (l) + sunlight → 6 C6H12O6 (s) + 6 O2 (g)
For every ______moles of carbon dioxide gas and ______moles of water, ______moles of glucose and ______moles of oxygen gas are formed. Carbon dioxide, water and sunlight are the ______of this reaction. Glucose and oxygen are the ______of this reaction.
Evaluating the Reaction
Evaluate the following reactions using the unit terms.
1 H2CO3 (aq) + heat → 1 CO2(g) + 1 H2O(l)
1. The reactants of this reaction are ______and ______.
2. The products of this reaction are ______and ______.
3. The only liquid in this equation is ______. The only gas in this equation is ______.
4. The substance that is dissolved in water is ______.
5. The 2 and 3 in H2CO3 are ______which indicate the number of element in the compound.
6. H2CO3 and heat are on the (left/right) side of the equations. Heat is a (reactant/product) which means that the reaction (releases/absorbs) heat from its surrounding. The reaction is (endothermic or exothermic).
3 Fe (s) + 2 CuCl2 (aq) → energy + 2 FeCl3 (aq) + 3 Cu (s)
7. The aqueous substances are ______and ______.
8. Energy is written on the ______and the reaction is ______.
Writing Formulas and Naming Compounds
The two types of compounds we will focus on first are ionic compounds (formed from positive and negative ions) and covalent compounds (molecular compounds). Identify the type of compound before you try to name it. [Note: + ion = “cation” and – ion = “anion”.]
Ionic / Covalent (nonmetals)Formula / cation (+ ion) before anion (– ion)
Examples: NaCl (NH4)2SO4 Al2S3 / usually the less electronegative atom is first
Examples: CO CO2 N2O
Naming / Name of cation + name of anion
Examples:
sodium chloride
ammonium sulfate
aluminum sulfide / Indicate the number (mono, di, tri, and kind of atoms). First element is simply name of element. Second element name ends with “ide”
Examples:
carbon monoxide carbon dioxide dinitrogen monoxide
Ionic Compounds
Cation / Anion / Formula / NameFe3+ / O2-
Co2+ / PO43+
(NH4)2S
Nickel (II) hydroxide
Al3+ / CO32+
Writing Chemical Equations
1. Aqueous silver (I) nitrate and aqueous sodium phosphate yields solid silver (I) phosphate and aqueous sodium nitrate.
2. Aqueous barium chloride and aqueous hydrogen sulfate yields barium sulfate precipitate and aqueous hydrochloric acid.
3. Aqueous manganese (II) chloride and aqueous potassium hydroxide yields solid manganese (II) hydroxide and aqueous potassium chloride.
4. Coleman stoves used for camping reacts butane (C4H10) in the presence of oxygen gas to produce carbon dioxide, water, and heat.
5. Cadmium (II) hydroxide is used in storage batteries. Aqueous cadmium (II) acetate and aqueous sodium hydroxide react to form cadmium (II) hydroxide precipitate and aqueous sodium acetate.
Balancing Chemical Reactions
The Law of Conservation of Mass states the matter is neither created nor destroyed in normal chemical reactions.
To observe the law of conservation of mass, ______ are added to balance the number of each substance. Coefficients represent the number of ______of each reactant and product.
Chemical reactions are accompanied by a change in energy. If energy is ______ by the reactants, energy is added to the ______as a reactant and the reaction is ______. If the chemical reaction ______energy, energy is added to the ______as a product and the reaction is ______.
1. ____ CO2 + _____ H2O + sunlight → ____ C6H12O6 + ____ O2 ______
2. ____ NH4OH + ____ H3PO4 → ____ (NH4)3PO4 + _____ H2O + heat ______
3. ____ Rb + ____ P → ____ Rb3P + heat ______
4. ____ C4H10 + ____ O2 → ____ CO2 + ____ H2O + heat ______
5. ____ Al(OH)3 + _____ H2SO4 → ____ Al2(SO4)3 + ____ H2O + energy ______
6. ____ Rb2S + heat → ____ Rb + _____ S8 ______
7. ____ KCl + ____H2O + heat → ____ KOH + ____ HCl ______
8. ____ H3PO4 + ____ Ca(OH)2 → ____ Ca3(PO4)2 + ____ H2O + heat ______
9. ____ NaCl + electricity ® ____ Na + _____ Cl2 ______
10. ____ Li + ____ H2O + heat → ____ LiOH + ____ H2 ______
7 diatomic elements: / P4 / S8Physical States / (s) / (l) / (g) / (aq)
Types of Reactions
The process by which one or more substances are changed into one or more different substances is a ______. The four ways of identifying chemical change are:
1.
2.
3.
4.
Types / Pattern / ExampleSynthesis / X + Y ® XY / 2H2 + 1 O2 ® 2H2O
Decomposition / AB ® A + B / 1 H2CO3 ® 1 H2O + 1 CO2
Single Replacement / XY + A ® AY + X / 1 Zn + 2 HCl ® 1 H2 + 1 ZnCl2
Double Replacement / XY + AB ® XB + AY / 2AgNO3 + 1 K2CrO4 ® 1 Ag2CrO4 + 2KNO3
Combustion / CxHy + O2 → CO2 + H2O / 1 CH4 + 2 O2 → 1 CO2 + 2 H2O
Synthesis
1. ____ Mg + ____ Cl2 →
2. ____ K2O + ____ CO2 →
3. ____ MgCl2 + ____ O2 →
4. ____ NaCl + ____ O2 →
5. ____ MgO + ____ H2O →
6. ____ NO2 + ____ H2O →
Decomposition
1. ____ KCl + electricity →
2. ____ Na2CO3 + heat →
3. ____ Cu(ClO3)2 + heat →
4. ____ LiOH + heat →
5. ____ H2CO3 + heat →
Single Replacement
1. ____ Cl2 + ____ NaF →
2. ____ Mg + ____ Al(OH)3 →
3. ____ K + _____ CuBr2 →
4. ____ Al + _____ H2O →
5. ____ H2 + _____ AgCl →
6. ____ F2 + _____ KBr →
7. ____ Rb + _____ HNO3 →
Combustion
A chemical reaction that combines oxygen with each of the other reactants is a ______.
1. ____ C6H6 + ____ O2 →
2. ____ C5H12 + ____ O2 →
3. ____ C6H14 + _____ O2 →
Double Replacement
A reaction in which two ions exchange places in a chemical reaction is a ______.
· Reactants must be dissolved in water (aqueous).
· One of the products must be a precipitate (solid), a gas, or water.
1. ____ BaCl2 (aq) + ____ AgNO3 (aq) →
2. ____ Pb(ClO3)2 (aq) + ____ KCl (aq) →
3. ____ K2S (aq) + ____ Cu(NO3)2 (aq) →
4. ____ H2SO4 (aq) + ____ NaOH (aq) →
5. ____ Na2CO3 (aq) + ___ MgCl2 (aq) →
6. ____ (NH4)3PO4 (aq) + Sr(NO3)2 (aq) →
Moles
There are exactly 12 grams of carbon-12 in one mole of carbon-12.
1 mole = molar mass = 6.02 x 1023 atoms, molecules, or formula units = 22.4 L of gas (STP)
Moles / Mass / Molecules / Volume at STP1.32 mol NaCl / 1.32 mol x 58.5 gNaCl1 mol NaCl= / 1.32 mol x (6.02 x 1023molecules)1 mol= / Sodium chloride is not a gas.
2.0 mol CO2 (6) / 64.0 grams CO2 / 64.0 g x (6.02 x 1023molecules)32.0 g= / 64.0 g x 22.4 L32 g = 44.8 L
4.5 mol NO2 (g)
2.5 mol CH4 (G)
Percent Composition
Water, H2O, for example has a molar mass of 18.02 g. The H’s mass is 2(1.0079) = 2.02 g. TheO’s mass is 16.00 g.
This is called the percent composition: H = = 0.112 = 11.2%. O = = 0.888 = 88.8%.
1. H2SO42. Ca(OH)2
3. HC2H3O2
Empirical and Molecular Formula
Empirical formula: the lowest whole number ratio of atoms in a compound.
Molecular formula: the true number of atoms of each element in the formula of a compound.
Empirical Molecular
Formula CH2O C6H12O6
Molar Mass 30.0 g 180 grams
Empirical Formula / Empirical Mass / Molecular Formula / Molecular MassCH / 78.0 grams/mol
NO2 / 92.0 grams/mol
CH2 / 84 grams/mol
Stoichiometry
______is the study of the relationship of substances in a chemical reaction. The ______is the ratio of substances based on a balanced equation.
1 C6H12O6 (s) + 6 O2(g) ® 6 CO2(g) + 6 H2O(l)
2.5 mole x moles
2.5 mole x grams
10 grams x moles
10 grams x grams
The coefficient indicate that for every one mole of C6H12O6 and ____ mole oxygen gas moles there are ______moles of carbon dioxide and ______moles of water. Using the reaction above:
1. Calculate the number of moles of carbon dioxide in 2.5 moles of C6H12O6 .
2. Calculate the mass of carbon dioxide in 2.5 moles of C6H12O6 .
3. Calculate the number of moles of carbon dioxide in 10 grams of C6H12O6 .
4. Calculate the mass of carbon dioxide in 2.5 moles of C6H12O6 .
5. Calculate the mass of water produced from 7.5 grams of oxygen gas.
6. Calculate the moles of oxygen gas produced from 100 grams of C6H12O6 .
7. Calculate the mass of water produced from 9.5 moles of oxygen gas.
8. Calculate the mass of carbon dioxide produced from 98 grams of oxygen gas.
Limiting Reagent
1. Consider the following reaction: 2 Al + 6 HBr → 2 AlBr3 + 3 H2
3.22 mole 4.96 mole
a. When 3.22 moles of Al reacts with 4.96 moles of HBr, how many moles of H2 are formed?
b. What is the limiting reactant?
c. For the reactant in excess, how many moles are left over at the end of the reaction?
2. Consider the reaction: _____ Al + _____ S8 → _____ Al2S3 25.0 grams 30 grams
a) If 25.0 g of aluminum and 30.0 g of sulfur are mixed, what is the limiting reactant?
b) How many grams of Al2S3 will be formed?
c) How many grams of the excess reactant will remain after the reaction is over?
Percent Yield
Actual yield is the amount of product measure in a laboratory experiment.
Theoretical yield is the amount of product that should be produced based on the chemical equation.
Percent yield is a calculation of how efficient or successful you were in performing the experiment.
3. Consider the reaction: 1 I2O5(g) + 5 CO(g) → 5 CO2(g) + 1 I2(g)
80.0 g 28.0 g
a. 80.0 grams of diiodine pentoxide, I2O5, reacts with 28.0 grams of carbon monoxide, CO. Determine the mass of iodine I2, which could be produced?
b. If, in the above situation, only 0.160 moles of I2 was produced.
i) What mass of iodine was produced?
ii) What percentage yield of iodine was produced?
Brinkmann 2011