Chapter 8 Quiz Review Flashcards
Using the law of conservation of mass, explain why the following reaction is wrong: HCl + Na(OH) –> NaCl
Conservation of mass - This is wrong because the H molecule and the OH molecule were completely destroyed. According to the conservation of mass, this cannot happen during a reaction (mass cannot be created or destroyed)
How can you tell when an equation is balanced?
You can tell an equation is balanced when the amount of each molecule is the same on both sides
State the law of conservation of mass.
Mass cannot be created nor destroyed in a chemical reaction.
What is a chemical reaction?
the process by which one or more substances change into one or more new substances
In a chemical reaction that releases energy, energy is a ________ of the reaction.
product
In a chemical reaction that absorbs energy, energy is a __________ of the reaction.
reactant
How does changing a coefficient differ from changing a subscript?
When you change the coefficients, you’re only multiplying the number of atoms of each element in the formula that follows. However, when you change the subscripts, you are changing the substance itself, which will make your chemical equation wrong.
Why is Fe balanced as 3Fe instead of Fe3?
If you change the subscript, you’re changing the chemical composition of Fe3
Which elements will always form a diatomic molecule in its elemental form?
H2, N2, O2, F2, Cl2, Br2, I2,
What are spectator ions?
Ions that do not participate in a reaction
What does ⇌ mean in a chemical reaction?
It replaces the yield sign for reversible reactions to reach equilibrium/gas state
What does Pt mean?
→
Used as a catalyst in the reaction/ reactant or product in aqueous solution
What does Δ mean?
→
The reaction is being heated
What does aqueous (aq) mean?
Dissolves in water
Define precipitate.
An insoluble solid formed from a chemical reaction
What is the purpose of balancing chemical equations?
To obey the law of conservation of mass
What does a catalyst do?
Increases the reaction rate
What do total ionic equations show?
They show all the soluble ions and insoluble solids, liquids, or gases in compounds.
What are the signs of a chemical change?
Odor
Color Change
Changes in temperature
Formation of a gas
Precipitate
What are reactants?
the starting substance in a chemical reaction
In an exothermic chemical reaction that releases energy, energy is a ____ of the reaction
product
What is a product?
the result of quantities being multiplied
In an endothermic chemical reaction that absorbs energy, energy is a _____ of the equation
reactant
Define solute.
one or more substances dissolved in a solution
Define solvent.
substance that dissolves a solute to form a solution
what does this sign symbolize: Δ
reactants are heated, the temperature is not specified
Examples of chemical change:
odor, color change, changes in temperature, formation of a gas, precipitate, bubbles
Examples of chemical reaction:
combustion, rusting, digestion, photosynthesis, baking, fermentation, washing, precipitate
chem reaction vs physical changes
Chemical change: new substance forms with properties that are different from the original substance(s).
Density
Boiling point
Melting point
Physical change: Changes of state are NOT chemical changes.
Evaporation
Condensation
Melting
Freezing
Examples of physical changes:
evaporation, condensation, melting, freezing, cutting
