Honors Chemistry - Reactions Quiz

• A chemical reaction is a change in the identity of a substance. A new substance is formed with different properties.
• One sign of a chemical reaction include a gas release. This sign is present through a gas rising up, bubbles, or an odor.
• Another sign of a chemical reaction includes a heat being produced. An Exothermic reaction gives off heat. In other words, heat is a product leaving the system. An Endothermic reaction absorbs heat. In other words, heat is a reactant. It feels cold afterward.
• Another sign of a chemical reaction is a color change. The new color should not be pre-existing.
• Lastly, another sign of a chemical reaction is a precipitate being formed. A precipitate is an insoluble solid falling out of a liquid.
• To read a chemical equation, the plus signs are read as "and" and the arrows are read as "react to form/yields."
• Aqueous solutions are solutions in which the solvent is water. The solutes have been dissolved in water. It functions as a liquid, but is not a pure substance liquid.
• A word equation uses chemical names to illustrate substances.
• A skeleton equation uses formulas. It doesn't necessarily have to be balanced.
• Chemical equations are balanced because of the Law of Conservation of Mass. The law states that atoms can't be created or destroyed in a chemical reaction. In other words, the number of atoms should be the same on the react and product side only in a closed system.
• When balancing chemical equations, never change a subscript to balance an equation as changing the formula changes the substance. Additionally, never put a coefficient in the middle of a formula.
• A synthesis reaction is when 2+ substances (metal + nonmetal) combine to make one compound.
• Synthesis Formula: A + B --> AB
• Decomposition reactions occur when one reactant breaks up into 2+ substances. Energy is usually required.
• Decomposition Formula: AB --> A + B
• Decomposition for Binary Compounds: decompose into those elements
• Decomposition for Carbonates: decompose into oxides and CO₂
• Decomposition for Hydroxides: decompose into oxides and water
• Open System: mass/matter/energy (heat, light) can flow into and out of an open system
• Closed System: matter can not flow into or out of a closed system, but heat energy can flow out of or into the system
• A combustion reaction occurs when a substance is burned in Oxygen gas. It generally requires heat.
• Combustion Formula: CₓHᵧ + O₂ --> CO₂ + H₂0
• Metal Combustion occurs when metals burn with O₂ to make oxides. It is the same as a synthesis reaction.
• A hydrocarbon is a compound composed of only C, H, and maybe O. Combustion products will be CO₂ and H₂O. It is known as complete combustion. Incomplete combustion makes CO.
• A Single Replacement reactions occurs when reactants are an element and a compound and products will be a different element and a different compound. One element replaces another, but the one that is higher on the activity series (more reactive) should not be alone.
• The Activity Series of Metals lists metals in order of reactivity. Higher on the list is more active and it is used to determine if rxn happens.
• The Activity Series of Halogens: lower mass halogen is more active, F replaces all, I does not replace
• Synthesis: If free metal is higher than cation in compound, reaction occurs. The free metal replaces cation.
• Synthesis: If free metal is lower than cation, no reaction.
• For Metal/Water Reactions, think of water as HOH. Metals replace one of the H, combine with hydroxide (OH⁻). H₂ is released.
• Halogen Reactions: Halogens are known to be very reactive. Halogen that is kicked out is diatomic element on other side because it is not capable of being on its own. Cations replace cations and anions replace anions.
• A Double Replacement reaction occurs when two compounds switch partners. The first on the left is the first on the right.
• Double Replacement Formula: AX + BY --> AY + BX
• In a double replacement reaction, reactants must be two ionic compounds or acids. It is usually in aqueous solution.
• Double Replacement reactions will only happen if one of the products is insoluble in water and forms a precipitate, a gas that bubbles out, or a liquid (usually water).
• Dissociation is when ionic compounds split into cations and anions. They are made into positive ions and negative ions. Generally occurs when dissolving in aqueous solution. Soluble molecular compounds do not dissociate (if soluble = polar, why they don't conduct electricity).
• Complete Ionic Equation:

  • If aqueous, write compound as its ions
  • If a solid, liquid, or gas, leave the formula as is
  • If you have a multiple of a molecule, the subscript becomes the coefficient
  • Distribute coefficient, like balancing
• Net Ionic Equations show what ions actually undergo a reaction. It does not include spectator ions.
• Spectator Ions appear on both sides of the equation (same state/charge on both sides). They are present in solution, but do not affect the reaction.
• Oxidation is the loss of electrons where the charge becomes more positive. The electrons have to go somewhere (where it is reduced).