Chapter 7 - Chemical Reactions
Redox reactions are responsible for the following reactions ...
- Rusting of Iron - Bleaching of Hair - Production of Electricity in batteriesaaaaa22a
Write a net ionic equation for the following: 2HBr (aq) + K2SO3 ----> H2O + SO2(g) + 2KBr
2HBr (aq) + K2SO3 ----> H2O + SO2(g) + 2KBr Complete Net Ionic Equation: H + Br + K + SO3 ----> H2O + SO2 + K + Br Spectator Ions: K and Br Net Ionic Equation: 2H + SO3 ---> H2O + SO2
Identify the spectator ions in the complete ionic equation. 2K+ (aq) + S^2- (aq) + Pb^2+ (aq) + 2NO3^- ---> PbS (s) + 2K+ (aq) + 2NO3^- (aq)
2K+ (aq) + S^2- (aq) + Pb^2+ (aq) + 2NO3^- ---> PbS (s) + 2K+ (aq) + 2NO3^- (aq) Spectator Ions: K+ and NO3^-
Write a generic equation for a synthesis or combination reaction.
A + B ----> AB
Write a generic equation for a single displacement reaction.
A + BC -----> AC + B
What makes a compound insoluble?
A compound is insoluble if it doe not dissolve in the liquid.
What is a displacement or single-displacement reaction?
A reaction where one element displaces another in a compound. Examples: Zn(s) + CuCl2(aq) -----> ZnCl2(aq) + Cu(s) Mg(s) + 2HCl(aq) ----> MgCl2(aq) + H2(g) 2Na(s) + 2H2O(l) ------> 2NaOH(aq) H2(g) A + BC -----> AC + B
Write a generic equation for a double-displacement reaction.
AB + CD -----> AD + CB
Write a generic equation for a decomposition reaction.
AB ----> A + B
What are the spectator ions in the following equation? Ag+ (aq) + NO3^- (aq) + Na+ (aq) + Cl^- (aq) ----> AgCl (s) + Na+ (aq) + NO3^- (aq)
Ag+ (aq) + NO3^- (aq) + Na+ (aq) + Cl^- (aq) ----> AgCl (s) + Na+ (aq) + NO3^- (aq) Unchanged (spectator Ions) = NO3^- and Na+
Write a balanced equation for the combustion of liquid propanol (C3H7OH).
C3H7OH (l) + O2 (g) ----> CO2 (g) + H2O (g) Balanced Equation 2C3H7OH (l) + 9O2 (g) ----> 6CO2 (g) + 8H2O (g)
Classify this reaction as synthesis, decomposition, single-displacement or double displacement. 2H2O2(aq) -----> 2H2O(l) + O2(g)
Decomposition - A complex substance decomposes to into simpler substances.
Classify this reaction as synthesis, decomposition, single-displacement or double displacement. Ba(NO3)2(aq) + K2SO4(aq) -----> BaSO4(s) + 2NO3(aq)
Double-displacement - Ba and K switch places to form two new compounds.
Type of Compound that undergo gas evolution reaction Reactant Type - carbonates and bicarbonates Intermediate Product - H2CO3 Gas Evolved - CO2
Example: 2HCl (aq) + K2CO3 (aq) ----> H2O (l) + CO2(g) + 2KCl (aq)
Type of Compound that undergo gas evolution reaction Reactant Type - Sulfides Intermediate Product - none Gas Evolved - H2S
Example: 2HCl (aq) + K2S (aq) -----> H2S (g) + 2KCl (aq)
Type of Compound that undergo gas evolution reaction Reactant Type - ammonium Intermediate Product - NH4OH Gas Evolved - NH3
Example: NH4Cl (aq) + KOH (aq) -----> H2O (l) + NH3 (g) + KCl (aq)
True/False - A chemical reaction occurred when silver nitrate was added to the water.
False
True/False - Acetone feels cold as it evaporates from the skin is a chemical reaction.
False
What are the four different types of chemical reactions?
Four different types of chemical reactions are 1) Precipitation Reactions 2) Acid-base Reactions 3) Gas Evolution Reactions (many gas evolution reactions are also acid-base reactions) 4) Oxidation-reduction (redox) Reactions * Combustion Reactions are a subset of Oxidation-reduction (redox) Reactions
What type of product do gas evolution reactions create?
Gas evolution reactions form gas as a product. Other gas evolution reactions form an intermediate product then decomposes into a gas.
Acid - Hydrobromic Acid
HBr
Write a molecular equations for the gas evolution that occurs when you mix aqueous hydrobromic acid and aqueous potassium sulfite. HBr (aq) + K2SO3 ----> H2SO3(aq) + KBr (aq) H2SO3 decomposes into SO2
HBr (aq) + K2SO3 ---> H2O(l) + SO2(g) + KBr Reactants: Products: 2 H 2 H 2 Br 2 Br 2 K 2 K 1 S 1 S 3 O 3 O 2HBr (aq) + K2SO3 ----> H2O + SO2(g) + 2KBr
Acid - Acetic Acid
HC2H3O2
Acid - Hydrochloric Acid
HCl
When a hydrochloric acid solution is combined with potassium hydroxide solution, an acid base reaction occurs. Write a balanced molecular equation and a net ionic equation for this reaction.
HCl (aq) + KOH (aq) ---> H2O + KCl The balanced molecular equation is: HCl (aq) + KOH (aq) ---> H2O (l) + KCl (aq) Complete Net Ionic Equation: H + Cl + K + OH ----> H2O + K + Cl Spectator Ions: K and Cl Net Ionic Equation: H + OH ---> H2O
Obtain the following information from the following equation: HCl (aq) + NaOH (aq) ----> H2O (l) + NaCl (aq) * Complete Ionic Equation * The spectator ions * Net Ionic Equation
HCl (aq) + NaOH (aq) ----> H2O (l) + NaCl (aq) Complete Ionic Equation: H + Cl- Na + OH ----> H2O + Na + Cl Spectator Ions = Cl and Na Net Ionic Equation: H + OH ---> H2O
Base - Lithium Hydroxide
LiOH
Write an equation for the precipitation reaction that occurs (if any) when solutions of lithium nitrate and sodium sulfate are mixed. LiNO3 (aq) + Na2SO4 (aq) -----> Potential insoluble products: LiSO4 NaNO3
NaNO3 is soluble. Li2SO4 is soluble. Both are soluble. No precipitation reaction.
Base - Sodium Hydroxide
NaOH
Is bubbles forming in a pot of boiling water evidence of a chemical reaction?
No, it is not evidence of a chemical reaction.
Classify this reaction as synthesis, decomposition, single-displacement or double displacement. 2Al(s) + Fe2O3(g) ----> Al2O3(s) + 2Fe(l)
Single-displacement - Al displaces Fe in Fe2O3
What is the fundamental definition of oxidation?
The fundamental definition of oxidation is the loss of electrons.
What is the fundamental definition of reduction?
The fundamental definition of reduction is the gain of electrons.
What is the net ionic equation for many acid-base reactions?
The net ionic equation for many acid-base reactions is H+ (aq) + OH-(aq) ---> H2O (l)
Balance the chemical equation: Fe(s) + HCl(aq) -----> FeCl3(aq) + H2(g) Reactants: 1 Fe atom 1 H atom 1 Cl atom Products: 1 Fe atom 2 H atoms 3 Cl atoms
To balance Cl at 3 in front of HCl(aq) Fe(s) + 3HCl(aq) -----> FeCl3(aq) + H2(g) New Reactants: 1 Fe atom 3 H atoms 3 Cl atoms To balance H atoms at (3/2) in front of H2(g) Fe(s) + 3HCl(aq) -----> FeCl3(aq) + (3/2) H2(g) New Products: 1 Fe atom 3 H atoms 3 Cl atoms Multiply out the fractions 2Fe(s) + 6HCl(aq) -----> 2FeCL3(aq) + 3H2(g) New Reactants: 2 Fe atom 6 H atoms 6 Cl atoms New Products: 2 Fe atom 6 H atoms 6 Cl atoms
True/False - A chemical reaction did occur when the solutions were combined.
True
True/False - Bubbling is observed when potassium carbonate and hydrochloric acid solutions are mixed is a chemical reaction.
True
True/False - Formation of a solid indicates a chemical reaction has occurred.
True
Is a beaker becoming hot to the touch after two solutions are mixed evidence of a chemical reaction?
Yes, it is evidence of a chemical reaction.
Is each compound soluble or insoluble? a) AgBr b) CaCl2 c) Pb(NO3)2 d) PbSO4
a) AgBr - Insoluble. Compounds containing Br are normally soluble, but Ag is an exception. b) CaCl2 - Soluble. Compounds containing Cl are normally soluble and Ca is not an exception c) Pb(NO3)2 - Soluble. Compounds containing NO3 are always soluble d) PbSO4 - Insoluble. Compounds containing SO4 are normally soluble, but Pb is an exception.
Which changes involve a chemical reaction. Explain your answers. a) butane burning in a butane lighter b) butane evaporating out of a butane lighter c) wood burning d) dry ice subliming
a) This is a chemical reaction. Both heat and light are emitted. b) This is not a chemical reaction. Gaseous and liquid butane are both butane. c) This is a chemical reaction. Both heat and light are emitted. d) This is not a chemical reaction. Solid dry ice is made of carbon dioxide, which sublimes (evaporates) as carbon dioxide gas.
What are the 4 different forms of chemical reactions?
1) Precipitation Reactions 2) Acid-Base Reactions 3) Gas Evolution Reactions 4) Oxidation-Reduction Reactions - Combustion Reactions are one type
What are the steps to write a balanced chemical equation?
1) Write a skeletal equation by writing correct chemical formulas for each reactants and products. 2) If an element occurs in only one compound on both sides of the equation, balance it first. If there is more than one such element, balance metals before nonmetals. 3) If an element occurs as a free element on either side of the chemical equation, balance it last. Always balance free elements by adjusting the coefficient on the free element. 4) If the balanced element equation contains coefficient fractions, change these into whole numbers by multiplying the entire equation by the appropriate factor. 5) Check to make certain the equation is balanced.
What is a balanced equation?
A balanced equation is a chemical formula in which the numbers of each type of atom on both sides of the equation are equal. To balance an equation, we insert coefficients (not subscripts) in front of the chemical formulas as needed to make the number of each type of atom in the reactants to equal to the number of each type of atom in products.
What is a chemical reaction?
A chemical reaction is the process by which one or more substances transform into different substances via a chemical change. Chemical reactions often emit or absorb energy.
What is a combustion reaction?
A combustion reaction is a reaction in which a substance reacts with oxygen emitting heat and forming one or more oxygen-containing compounds.
What is a complete ionic equation?
A complete ionic equation is a chemical equation showing all species as they are actually present in the solution. This equation shows the reactants and products as they are actually present in a solution.
What makes a compound soluble?
A compound is soluble in a particular liquid if it dissolves in that liquid.
What is a gas evolution reaction?
A gas evolution reaction is a reaction that occurs in a solution and forms a gas as one of its products.
What is a molecular equation?
A molecular equation is chemical equation showing the complete neutral formulas for every compound in a reaction.
What is net ionic equation?
A net ionic equation is an equation that shows only the species that actually participate in a reaction.
What is a precipitate?
A precipitate is an insoluble product formed through the reaction of two solutions containing soluble compounds. A precipitate is a solid.
What is a precipitation reaction?
A precipitation reaction is a reaction that forms a solid or precipitate when two aqueous solutions are mixed.
What is a precipitation reaction?
A reaction that forms from a solid upon mixing two aqueous solutions. Only insoluble compounds form precipitates. Precipitation reactions do not always occur when mixing two aqueous solutions. Only insoluble compounds form precipitates. In a precipitate reaction two soluble compounds combine to form an insoluble compound (precipitate).
What is a decomposition reaction?
A reaction when a complex substance decomposes to form simpler substances. These reactions require energy in the form of heat, electrical current or light. Examples: 2H2O(s) -----> 2H2(g) + O2(g) CaCO3(s) -----> CaO(s) + CO2(g) 2HgO(s) -----> 2Hg(l) + O2(g) AB -----> A + B
What is a synthesis or combination reaction?
A reaction when simpler substances combine to form more complex substances. Examples: 2Na(s) + Cl2(g) ----> 2NaCl(s) CaO(s) + CO2(g) ----> CaCO3(s) A + B ----> AB
What is a double-displacement reaction?
A reaction where two elements or groups or elements in two different compounds exchange places to form two new compounds. Examples: AgNO3(aq) + NaCl(aq) ----> AgCl(s) + NaNO3(aq) HCl(aq) + NaOH(aq) -----> H2O(l) + NaCl(aq) AB + CD -----> AD + CB
What is a solubility rule?
A solubility rule is a set of empirical rules used to determine whether an ionic compound is soluble.
What is a strong electrolyte?
A strong electrolyte is a substance whose aqueous solutions are good conductors of electricity.
What is a strong electrolyte solution?
A strong electrolyte solution is a solution containing a solute that dissociates into ions; therefore, a solution that conducts electricity well.
What is a combustion reaction?
A type of redox reaction. Combustion reactions are characterized the reaction of a substance with O2 to form one or more oxygen-containing compounds, often including water. Combustion reactions are exothermic -the emit heat.
What is another acid-base reaction involving a salt?
Acid + Base ----> Water + Salt
What is the net ionic equation of the following equation? Ag+ (aq) + NO3^- (aq) + Na+ (aq) + Cl^- (aq) ----> AgCl (s) + Na+ (aq) + NO3^- (aq)
Ag+ (aq) + NO3^- (aq) + Na+ (aq) + Cl^- (aq) ----> AgCl (s) + Na+ (aq) + NO3^- (aq) Remove spectator ions: NO3^- and Na+ Ag+ (aq) + Cl- ----> AgCl (s)
Pair each cation on the left with an anion on the right that will form an insoluble compound with it and write a formula for the insoluble compound. Use each anion only once. Ag+ SO4^2- Ba^2+ Cl- Cu^2+ CO3^2- Fe^3+ S^2-
AgCl BaSO4 CuCO3 Fe3S3
What is the complete ionic equation of AgNO3 (aq) + NaCl (aq) ----> AgCl (s) + NaNO3 (aq)?
AgNO3 (aq) + NaCl (aq) ----> AgCl (s) + NaNO3 (aq) Net ionic equation: Ag+ (aq) + NO3^- (aq) + Na+ (aq) + Cl^- (aq) ----> AgCl (s) + Na+ (aq) + NO3^- (aq)
What is an acid-base reaction (also called a neutralization reaction)?
An acid base reaction is a reaction that forms water and typically a salt. The salt is an ionic compound that usually remains dissolved.
What is an acid-base reaction?
An acid-base reaction are reactions that form water upon mixing of an acid and a base.
What is an aqueous solution?
An aqueous solution is a homogeneous mixture of a substance with water.
What is an oxidation-reduction (redox) reaction?
An oxidation-reduction (redox) reaction is a reaction in which electrons are transferred from one substance to another.
Base - Barium Hydroxide
Ba(OH)2
Write a balanced equation for the combustion of liquid pentane (C5H12), a component in gasoline.
C5H12 (l) + O2 (g) ----> CO2 + H2O Balanced Equation C5H12 (l) + 8O2 (g) ----> 5CO2 + 6H2O
Write a balanced equation for the combustion of liquid methyl alcohol (CH3OH). CH3OH(l) + O2(g) ----> CO2(g) + H2O(g) Balance the equation
CH3OH(l) + O2(g) ----> CO2(g) + H2O(g) 2H2OH(l) + 3O2 ----> 2CO2(g) + 4H2O(g)
Base - Calcium Hydroxide
Ca(OH)2
Consider this reaction occurring in aqueous solution. 2HBr (aq) + Ca(OH)2 (aq) ----> 2H2O (l) + CaBr2 (aq) Separate aqueous ionic compounds into their constituent ions. The 2H2O (i) remains as one unit. Complete Ionic Equation: 2H (aq) + 2Br (aq) + Ca (aq) + 2OH ---> 2H2O (l) + Ca (aq) + 2Br (aq) Find Net Ionic Equation - Minus Out Duplicates
Complete Ionic Equation: 2H (aq) + 2Br (aq) + Ca (aq) + 2OH ---> 2H2O (l) + Ca (aq) + 2Br (aq) Find Net Ionic Equation: 2H (aq) + 2OH ---> 2H2O (l) (divide out 2) H (aq) + OH ----> H2O (l)
Type of Compound that undergo gas evolution reaction Reactant Type - sulfites and bisulfates Intermediate Product - H2SO3 Gas Evolved - SO2
Example: 2HCl (aq) + K2SO3 (aq) -----> H2O (l) + SO2 (g) + 2KCl (aq)
True/False - Heat is felt when a warm object is placed in your hand is a chemical reaction.
False
True/False - The initial disappearance of silver nitrate in water indicates a chemical reaction has occurred.
False
True/False - The lack of temperature change indicates a chemical reaction didn't occur.
False
Consider this precipitation reaction occurring in aqueous solution. Pb(NO3)2 (aq) + 2LiCL (aq) ----> PbCl2 (s) + 2LiNO3 (aq) Write the complete ionic equation and a net ionic equation for the reaction. Separate aqueous ionic compounds into their constituent ions. The PbCl2 (s) remains as one unit. Complete Ionic Equation Pb2 (aq) + 2NO3 (aq) + 2Li (aq) + 2Cl (aq) ---> PbCl2 (s) + 2Li (aq) + 2NO3 (aq) Find Net Ionic Equation - Minus Out Duplicates
Find Net ionic equation: Pb2 (aq) + 2NO3 (aq) + 2Li (aq) + 2Cl (aq) ---> PbCl2 (s) + 2Li (aq) + 2NO3 (aq) Complete Ionic Equation Pb2 (aq) + 2NO3 (aq) + 2Li (aq) + 2Cl (aq) ---> PbCl2 (s) + 2Li (aq) + 2NO3 (aq) Net Ionic Equation Pb2 (aq) + 2Cl (aq) ----> PbCl2 (s)
Acid - Sulfuric Acid
H2SO4
Write molecular and a net ionic equation for the reaction that occurs between H2SO4 (aq) and KOH (aq)
H2SO4 (aq) and KOH (aq) H2SO4 + KOH ----> H2O + K2SO4 Balance the Equation: Molecular Equation: H2SO4 (aq) + 2KOH (aq) ----> 2H2O (l) + K2SO4 (aq) Complete Net Ionic Equation H + SO4 + K + OH ----> H2O + K + SO4 Spectator Ions = SO4 and K Net Ionic Equation: H + OH ---> H2O
Acid - Perchloric Acid
HClO4
Acid - Nitric Acid
HNO3
Write a molecular and a net ionic equation for the reaction between aqueous HNO3 and aqueous Ca(OH)2. HNO3 (aq) + Ca(OH)2 (aq) ---> H2O (l) + Ca(NO2)3 (aq) Balance the Equation: Reactants: 3 H atoms 1 N atom 5 O atoms 1 Ca atom Products: 2 H atoms 3 N atoms 1 O atom + 6 O atoms = 7 atoms 1 Ca atom
HNO3 (aq) + Ca(OH)2 (aq) ---> H2O (l) + Ca(NO2)3 (aq) 2 HNO3 (aq) + Ca(OH)2 (aq) ----> 2H2O (l) + Ca(NO3)2 (aq) Net Ionic Equation: 2H + 2N + 6O + Ca + 2O + 2H ----> 2H2O (l) + Ca + 2N + 6O Net Ionic Equation. 2H + Ca + 2OH ----> 2H2O (l)
Write a molecular equation for the gas evolution that occurs when you mix aqueous nitric acid and aqueous sodium carbonate. HNO3 (aq) + Na2CO3 (aq) -----> H2CO3 (aq) + NaNO3 (aq) H2CO3 (aq) decomposes into CO2 (g)
HNO3 (aq) + Na2CO3(aq) --> H2O (l) + CO2(g) NaNO3 (aq) Balance the equation: 2HNO3(aq) + Na2CO3(aq) --> H2O(l) + CO2(g) + 2NaNO3(aq)
Base - Potassium Hydroxide
KOH
These compounds are mostly soluble: Li+, Na+, K+, NH4+, NO3-, C2H3O2-, Cl-, Br-, I-, SO42-
Li+, Na+, K+, or NH4+, NO3, C2H3O2 - no exceptions Cl, Br or I - Exceptions contains Ag, Hg, Pb - insoluble SO4 - Exceptions contains Ca, Sr, Ba, Pb - insoluble
Write an equation for the precipitation reaction (if any) that occurs when solutions or lead(II) acetate and sodium sulfate are mixed. Pb(C2H3O2)2 (aq) + Na2SO4 (aq) ----> Potential insoluble products: PbSO4 NaC2H3O2 Pb(C2H3O2)2 (aq) + Na2SO4 (aq) --> PbSO4 + NaC2H3O2 Reactants: 1 Pb atom 4 C atoms 6 H atoms 4 O atoms + 4 O atoms = 8 O atoms 2 Na atoms 1 S atom Products: 1 Pb atom 2 C atoms 3 H atoms 4 O atoms + 2 O atoms = 6 O atoms 1 Na atom 1 S atom
NaC2H3O2 is soluble since Na is always soluble. PbSO4 is insoluble. SO4 is normally soluble, but Pb is an exception. Pb(C2H3O2)2 (aq) + Na2SO4 (aq) --> PbSO4 + 2NaC2H3O2 New Products: 1 Pb atom 4 C atoms 6 H atoms 4 O atoms + 4 O atoms = 8 O atoms 2 Na atom 1 S atom
Write an equation for the precipitation reaction that occurs (if any) when solutions of sodium carbonate and copper (II) chloride are mixed. Na2CO3 (aq) + CuCl2 (aq)----> List the potentially insoluble products: NaCl CuCO3 Na2CO3 (aq) + CuCl2 (aq) ----> CuCO3 + NaCl Reactants: 2 Na atoms 1 C atom 3 O atoms 1 Cu atom 2 Cl atoms Products: 1 Na atom 1 C atom 3 O atoms 1 Cu atom 1 Cl atom
NaCl is soluble. CuCO3 is insoluble. Since this example has in insoluble product, you proceed to the next step. Balance the equation Na2CO3 (aq) + CuCl2 (aq) ----> CuCO3 + 2NaCl New Products: 2 Na atom 1 C atom 3 O atoms 1 Cu atom 2 Cl atom
Write a balanced equation for the combustion reaction between liquid octane (C8H18), a component of gasoline, and gaseous oxygen to form gaseous carbon dioxide and gaseous water. C8H18 + O2(g) ----> CO2(g) + H2O(g) Balance the equation: Reactants: 8 C atoms 18 H atoms 2 O atoms Products: 1 C atom 3 O atoms 2 H atoms
No atoms are in balance. To balance C, put an 8 before CO2(g) C8H18 + O2(g) ----> 8CO2(g) + H2O(g) New Products: 8 C atoms 16 O atoms + O = 17 O atoms 2 H atoms To balance H, put 9 in front of H2O(g) C8H18 + O2(g) ----> 8CO2(g) + 9H2O(g) New Products: 8 C atoms 16 O atoms + 9 O = 25 O atoms 18 H atoms To balance O put 25/2 before O2 C8H18 + (25/2)O2(g) ----> 8CO2(g) + 9H2O(g) Reactants: 8 C atoms; 16 C atoms 18 H atoms; 36 atoms 25 O atoms; 50 atoms Products: 8 C atoms; 16 C atoms 18 H atoms; 36 atoms 16 O atoms + 9 O atoms = 25 O atoms; 50 atoms Need to multiply out fractions: 2C8H18 + 25O2(g) ----> 16CO2(g) + 18H2O(g)
Is water condensing evidence of a chemical reaction?
No, it is not evidence of a chemical reaction.
Pb(NO3)2(aq) + 2LiCl(aq) ----> PbCl2(s) + 2LiNO3(aq) Is this a redox reaction?
No, this is a precipitation reaction.
2HBr(aq) + Ca(OH)2(aq) ----> 2H2O(l) + CaBr2(aq) Is this a redox reaction?
No, this is an acid-base reaction.
These compounds are mostly insoluble: OH- S2- CO32- PO43-
OH- Exceptions Li+, Na+, K+, or NH4+ S2 - Exceptions - Li+, Na+, K+, or NH4+, Ca, Sr, Ba CO3 or PO4 - Exceptions Li+, Na+, K+, or NH4+
OIL RIG LEO GER
OIL RIG - Oxidation is Loss; Reduction is Gain LEO GER Lose Electrons Oxidation; Gain Electrons Reduction
What shows that a chemical reaction has occurred?
Only chemical analysis shows that the initial substances have changed into other substances conclusively proves that a chemical reaction has occurred. Chemical reactions may occur without any obvious signs, yet chemical analysis may show that a reaction has indeed occurred. Color changes, formation of a solid, formation of a gas, heat absorption or emission and light emission are evidence that a chemical reaction as occurred.
What are oxidation-reduction reactions or redox reactions?
Oxidation-reduction reaction or redox reactions are reactions in which electrons are transferred from one substance to another. Oxidation and reduction must occur together.
In photosynthesis, plants make sugar glucose, C6H12O6, from carbon dioxide and water. The equation for the reaction is: 6 CO2 + 6 H2O ----> C6H12O6 + xO2 In order for this equation to be balanced, the coefficient x must be: a) 3 b) 6 c) 9 d) 12
Reactants: 6 C atoms 12 O atoms + 6 O atoms = 18 O atoms 12 H atoms Products: 6 C atoms 6 O atoms + ? O atoms 12 H atoms Answer b) 6
Redox reactions are those in which the following occur:
Redox (or oxidation-reduction) reactions are those in which the following occur: - A substance reacts with elemental oxygen - A metal reacts with a nonmetal - More generally, one substance transfers electrons to another substance.
2Al(s) + 3Sn(aq) -----> 2Al(aq) + 3Sn(s) Is this a redox reaction?
Redox Reaction
C(s) + O2(g) ----> CO2(g) Is this a redox reaction?
Redox Reaction
2Li(s) + Cl2(g) ----> 2LiCl(s) Is this a redox reaction?
Redox Reaction -
2Mg(s) + O2(g) ---> 2MgO(s) Is this a redox reaction?
Redox Reaction - Mg reacts with elemental oxygen
Zn(s) + Fe(aq) -----> Zn(aq) + Fe (s) Is this a redox reaction?
Redox reaction - Zn transfers two electrons to Fe
Ca(s) + Cl2(g) ----> CaCl2(s) Is this a redox reaction?
Redox reaction - a metal reacts with a nonmetal
Write a balanced equation for the reaction between between solid silicon dioxide and solid carbon to produce solid silicon carbide and carbon monoxide gas. SiO2(s) + C(s) ----> SiC(s) + CO(g) Balance the equation Reactant: 1 Si atom 2 O atoms 1 C atom Products: 1 Si atom 1 O atom 2 C atoms
Si atoms are in balance. To balance the O atoms put a 2 before 2CO(g). Products: 1 Si atom 3 C atoms 2 O atoms To balance the C atoms put a 3 before C(s). New equation: SiO2(s) + 3C(s) ----> SiC(s) + 2CO(g) Reactants: 1 Si atom 2 O atoms 3 C atoms Products: 1 Si atom 2 O atoms 3 C atoms The equation is balanced.
What are spectator ions?
Spectator ions are ions that do not participate in a reaction; they appear unchanged on both sides of a chemical reaction.
Classify this reaction as synthesis, decomposition, single-displacement or double displacement. Ca(s) + Cl2(g) ----> CaCl2(s)
Synthesis - A more complex substance forms from two simpler ones.
Classify this reaction as synthesis, decomposition, single-displacement or double displacement. Na2O(s) + H2O(l) ----> 2NaOH(aq)
Synthesis - a more complex substance was formed from two simpler substances.
Balance the chemical equation: HCl(g) + O2(g) -----> H2O(l) + Cl2(g) Reactant: 1 H atom 1 Cl atom 2 O atoms Products: 2 H atoms 1 O atom 2 Cl atoms
To balance H, add 2 in front of HCl(g) 2HCl(g) + O2(g) -----> H2O(l) + Cl2(g) New Reactants: 2 H atom 2 Cl atom 2 O atoms To balance O, add (1/2) in front of O2 2HCl(g) + (1/2)O2(g) -----> H2O(l) + Cl2(g) Multiply out the fractions 4HCl(g) + O2(g) ------> 2H2O(l) + 2Cl2(g) Reactant: 4 H atom 4 Cl atom 2 O atoms Products: 4 H atoms 2 O atom 4 Cl atoms
Write a balanced equation for the reaction of a solid aluminum with aqueous sulfuric acid to form aqueous aluminum sulfate and hydrogen gas. Al(s) + H2SO4(aq) ----> Al2(SO4)3(aq) + H2(g) Reactants: 1 Al atom 2 H atoms 1 S atom 4 O atoms Products: 2 Al atoms 3 S atoms 12 O atoms 2 H atoms
To balance S, add 3 to front H2SO4(aq) Al(s) + 3H2SO4(aq) ----> Al2(SO4)3(aq) + H2(g) Reactant: 1 Al atoms 6 H atoms 3 S atoms 12 O atoms Products 2 Al atoms 2 H atoms 3 S atoms 12 O atoms To balance Al add 2 to Al(s) 2Al(s) + 3H2SO4(aq) ----> Al2(SO4)3(aq) + H2(g) To balance H add 3 to H2(g) 2Al(s) + 3H2SO4(aq) ----> Al2(SO4)3(aq) + 3H2(g) Reactant: 2 Al atoms 6 H atoms 3 S atoms 12 O atoms Products 2 Al atoms 6 H atoms 3 S atoms 12 O atoms
Write a balanced equation for the reaction of aqueous lead (II) acetate with aqueous potassium iodide to form solid lead (II) iodide and aqueous potassium acetate. Pb[C2H3O2]2(aq) + KI(aq) ----> PbI2 + KC2H3O2(aq) Reactants: 1 Pb atom 4 C atoms 6 H atoms 4 O atoms 1 K atom 1 I atom Products: 1 Pb atom 2 C atoms 3 H atoms 2 O atoms 1 K atom 2 I atoms
To balance, C atoms put a 2 before KC2H3O2(aq) Pb[C2H3O2]2(aq) + KI(aq) ----> PbI2 + 2KC2H3O2(aq) New Products: 1 Pb atom 4 C atoms 6 H atoms 4 O atoms 2 K atom 2 I atoms To balance K & I add 2 in front of KI(aq) Pb[C2H3O2]2(aq) + 2KI(aq) ----> PbI2 + 2KC2H3O2(aq) New Reactants: Reactants: 1 Pb atom 4 C atoms 6 H atoms 4 O atoms 2 K atoms 2 I atoms
True/False - Propane forms a flame and emits heat as it burns is a chemical reaction.
True
True/False - The color change of the solution indicates a chemical reaction has occurred.
True
Vinegar forms bubbles when it is poured onto calcium deposits on a faucet,and some of the calcium dissolves. Has a chemical reaction occurred? Explain your answer.
Yes a chemical reaction has occurred. The presence of the bubbles is evidence for the formation of a gas.
Is a cloudy solution becoming clear upon adding it to another solution evidence of a chemical reaction?
Yes, it is evidence of a chemical reaction.
Is bubble formation on chalk added to an acid evidence of a chemical reaction?
Yes, it is evidence of a chemical reaction.
Is formation of a gas when you add a substance to a solution evidence of a chemical reaction?
Yes, it is evidence of a chemical reaction.
Is the emission of light evidence of a chemical reaction?
Yes, it is evidence of a chemical reaction.
Is the emission or absorption of heat evidence of a chemical reaction?
Yes, it is evidence of a chemical reaction.
Classify each reaction as a synthesis, decomposition, single-displacement or double-displacement reaction. a) 2Al(s) + 2H3PO4 (a1) ---> 2AlPO4 + 3H2 (g) b) CuSO4 (aq) + 2KOH (aq) -----> Cu(OH)2 (s) + K2SO4 (aq) c) 2K (s) + Br2 (l) ----> 2KBr (s) d) CuCl2 (aq) --- electric current ---> Cu(s) + Cl2 (g)
a) 2Al(s) + 2H3PO4 (a1) ---> 2AlPO4 + 3H2 (g) Single-Displacement b) CuSO4 (aq) + 2KOH (aq) -----> Cu(OH)2 (s) + K2SO4 (aq) Double-Displacement c) 2K (s) + Br2 (l) ----> 2KBr (s) Synthesis d) CuCl2 (aq) --- electric current ---> Cu(s) + Cl2 (g) Decomposition
Which reactions are redox (oxidation-reduction) reactions? a) Ba(NO3)2 (aq) + K2SO4 (aq) ----> BaSO4 + 2KNO3 b) Ca (s) + Cl2 (g) ----> CaCl2 (s) c) HCl (aq) + NaOH (aq) ----> H2O (l) + NaCl (aq) d) Zn (s) + Fe^2+ (aq) ----> Zn^2+ (aq) + Fe (s)
a) Ba(NO3)2 (aq) + K2SO4 (aq) ----> BaSO4 + 2KNO3 Precipitate Reaction b) Ca (s) + Cl2 (g) ----> CaCl2 (s) Redox Reaction c) HCl (aq) + NaOH (aq) ----> H2O (l) + NaCl (aq) Acid-Base Reaction d) Zn (s) + Fe^2+ (aq) ----> Zn^2+ (aq) + Fe (s) Redox Reaction
Is each compound soluble or insoluble? a) CuS b) FeSO4 c) PbSO3 d) NH4Cl
a) CuS - Insoluble. It contains S which is insoluble. Cu is not an exception. b) FeSO4 - Soluble. It contains SO4 - Fe is not an exception c) PbSO3 - Insoluble. It contains SO3 which is soluble, but Pb is an exception. d) NH4Cl - Soluble. It contains NH4.
Is each compound soluble or insoluble? For the soluble compounds identify the ions present in each solution. a) NaC2H3O2 b) Sn(NO3)2 c) AgI d) Na3(PO4)
a) NaC2H3O2 Soluble - It contains Na+ b) Sn(NO3)2 Soluble - It contains NO3- c) AgI Insoluble - It contains I- which is typcially soluble, but combined with Ag+ makes it insoluble. d) Na3(PO4) Soluble - It contains Na+
Which of these reactions results in the formation of a precipitate? a) NaNO3 (aq) + CaS (aq) b) MgSO4 (aq) + CaS (aq) c) NaNO3 (aq) + MgSO4 (aq)
a) NaNO3 (aq) + CaS (aq) Products: NaS - soluble; CaNO3 - soluble b) MgSO4 (aq) + CaS (aq) Products: MgS - insoluble; CaSO4 - insoluble c) NaNO3 (aq) + MgSO4 (aq) Products: NaSO4 - soluble; MgNO3 - soluble The answer is B
Which observations is consistent with a chemical reaction occurring? Why? a) Solid copper deposits on a piece of aluminum foil when the foil is placed in a blue copper nitrate solution. The blue color of the solution fades. b) Liquid ethyl alcohol turns into a solid when placed in a low-temperature freezer. c) A white precipitate forms when solutions of barium nitrate and sodium sulfate are mixed. d) A mixture of sugar and water bubbles when yeast are added. After several days, the sugar is gone and the ethyl alcohol is found in the water.
a) This is a chemical reaction. There is a color change showing a chemical reaction. b) This not a chemical reaction. The state of the compound change, but no chemical reaction takes place. c) This a chemical reaction. There is a formation of a solid in a previously clear solution. d) This a chemical reaction. There is a formation of a gas went the yeast is added to the solution.
Which changes involve a chemical reaction? Explain your answers. a) ice melting upon warming b) an electric current passing through water, resulting in the formation of hydrogen and oxygen gas that appears as bubbles rising in the water. c) iron rusting d) bubbles forming when a soda can is opened
a) This is not a chemical reaction. Melting ice forms water, but both ice and water are composed of water molecules. b) This is a chemical reaction. Water decomposes into hydrogen and oxygen, as evidenced by the bubbling. c) This is a chemical reaction. Iron changes into iron oxide, changing color in the process. d) This is not a chemical reaction. Even though there is bubbling, it is just carbon dioxide coming out of the liquid.
Which quantity must always be the same on both sides of a balanced chemical equation? a) the number of each type of atom b) the number of each type of molecule c) the sum of all of the coefficients
a) the number of each type of atom Since the molecules change during a chemical reaction, their number is not the same on both sides nor is the sum of all of the coefficients the same.
Precipitation reactions and acid-base reactions can both also be classified as: a) Synthesis reactions b) Decomposition reactions c) Single-Displacement reactions d) Double-Displacement reactions
d) Double-Displacement reactions In a precipitation reaction, cations and anions "exchange partners" to produce at least one product. In acid-base reaction, H+ + OH- combine to form water and their partners pair off to a salt.
What are the abbreviations for reactants and products states in chemical equations?
gas - (g) liquid - (l) solid - (s) aqueous (water solution) - (aq)
