AP Chemistry:: Chemical Reactions

What is the LAW OF CONSERVATION OF MASS, and how does it apply to a chemical reaction?

- **A)** This law has no actual relationship to the total mass of reactants compared to products in a chemical reaction
- **B)** The law of conservation of mass states that mass can be freely created or destroyed during a chemical reaction, with no requirement that reactant and product mass match
- **C)** Conservation of mass requires that the total mass of PRODUCTS always be GREATER than the total mass of REACTANTS in any chemical reaction
- **D)** MATTER cannot be CREATED or DESTROYED in a chemical reaction -- the total MASS of all REACTANTS must equal the total mass of all PRODUCTS

What does it mean to BALANCE a chemical equation, and why is this necessary?

- **A)** Adjusting the COEFFICIENTS in front of each chemical formula so that the SAME number of each type of ATOM appears on both the reactant and product sides -- necessary to satisfy the law of conservation of mass
- **B)** Balancing a chemical equation means changing the SUBSCRIPTS within a chemical formula, rather than adjusting the coefficients in front of each formula
- **C)** A balanced chemical equation always has a DIFFERENT total number of atoms on the reactant side compared to the product side
- **D)** This process has no actual relationship to ensuring the same number of each atom type appears on both sides of an equation

What is a SYNTHESIS (or combination) reaction, as one of the general reaction TYPES?

- **A)** A reaction in which TWO OR MORE simpler substances COMBINE to form ONE more complex product (general form: A + B -> AB)
- **B)** This reaction type has no actual relationship to multiple substances combining to form a single product
- **C)** A synthesis reaction refers to ONE complex substance BREAKING DOWN into two or more simpler products, rather than simpler substances combining
- **D)** A synthesis reaction always produces MORE separate products than the number of reactants that combined to form them

What is a DECOMPOSITION reaction, as another general reaction type, and how does it CONTRAST with a synthesis reaction?

- **A)** This reaction type has no actual relationship to a single substance breaking down into simpler products
- **B)** Decomposition reactions always produce FEWER total product substances than the single reactant that broke down
- **C)** A reaction in which ONE complex substance BREAKS DOWN into two or more SIMPLER products (general form: AB -> A + B) -- the OPPOSITE pattern of a synthesis reaction, which combines simpler substances into one
- **D)** A decomposition reaction refers to multiple simpler substances combining into one complex product, identical to a synthesis reaction

What is a SINGLE REPLACEMENT (single displacement) reaction, as another general reaction type?

- **A)** A reaction in which ONE element REPLACES another element within a compound (general form: A + BC -> AC + B)
- **B)** This reaction type has no actual relationship to one element replacing another element within a compound
- **C)** A single replacement reaction refers to TWO different compounds exchanging their component elements/ions with each other, rather than one element replacing another within a single compound
- **D)** Single replacement reactions always involve exactly FOUR different reactant substances, rather than a single element reacting with a single compound

What is a DOUBLE REPLACEMENT (double displacement) reaction, and how does it differ from a SINGLE replacement reaction?

- **A)** A reaction in which TWO compounds EXCHANGE their component ions/elements with each other (general form: AB + CD -> AD + CB) -- unlike single replacement, where only ONE free element displaces another within a compound
- **B)** A double replacement reaction involves only ONE free element displacing another element within a single compound, identical to single replacement
- **C)** Double replacement reactions always involve exactly TWO reactant substances combining into ONE single product, identical to a synthesis reaction
- **D)** This reaction type has no actual relationship to two compounds exchanging their component ions with each other

What is a COMBUSTION reaction, and what are the TYPICAL products when a HYDROCARBON (a compound containing only carbon and hydrogen) undergoes complete combustion?

- **A)** This reaction type has no actual relationship to a hydrocarbon reacting with oxygen to release energy
- **B)** Combustion reactions never actually involve oxygen as a reactant, with no relationship to producing carbon dioxide or water
- **C)** Complete combustion of a hydrocarbon typically produces PURE CARBON and HYDROGEN GAS as products, rather than carbon dioxide and water
- **D)** A reaction in which a substance reacts rapidly with OXYGEN, typically releasing energy as heat and light; complete combustion of a hydrocarbon typically produces CARBON DIOXIDE (CO2) and WATER (H2O) as products

What is a PRECIPITATION reaction, as a specific type of double replacement reaction occurring in AQUEOUS (water-based) solution?

- **A)** A reaction in which two AQUEOUS (dissolved) ionic solutions are mixed, and an INSOLUBLE solid product (a 'precipitate') forms and separates out of the solution
- **B)** Precipitation reactions always occur only between two GASES, never between two aqueous ionic solutions
- **C)** This reaction type has no actual relationship to an insoluble solid forming when two aqueous solutions are mixed
- **D)** A precipitation reaction refers to a solid dissolving completely into an aqueous solution, rather than a solid forming and separating OUT of solution