Unit 1: Topic 2 Chemical Reactions Flashcards
What are the three steps of a chemical reaction?
- Breaking of bonds in reactants
- Interaction between atoms and molecules
- Formation of new atomic and molecular products
What is the difference between a chemical reaction and a phase change?
A chemical reaction involves the formation of new substances, while a phase change only involves a change of state (e.g., solid to liquid) without forming new substances.
Q: What are signs that a chemical reaction has occurred?
Temperature change
Emission of light
Formation of gas
Formation of a precipitate
Color change
What do the state symbols in a chemical equation represent?
(s) = Solid
(l) = Liquid
(g) = Gas
(aq) = Aqueous (dissolved in water)
Q: How do you write a chemical equation?
: A chemical equation must include:
One or more reactants
One or more products
An arrow showing the direction of the reaction
State symbols (s), (l), (g), (aq)
Q: What is the law of conservation of mass?
The Law of Conservation of Mass states that mass cannot be created or destroyed in a chemical reaction. The total mass of the reactants is always equal to the total mass of the products.
Q: What are the main types of chemical reactions?
Synthesis (Combination)
Decomposition
Single Displacement
Double Displacement
Combustion
Acid-Base
Redox
Q: What is a single displacement reaction, and what is its general form?
A: A more reactive element replaces a less active element in a compound.
General Form: A + BC -> AC + B
Example: Fe + CuSO₄ -> FeSO ₄ + Cu
Q: What is a decomposition reaction, and what is its general form?
A: A single compound breaks down into two or more simpler substances.
General Form: AB -> A + B
Example 2H₂O₂ -> 2H₂O + O₂
What is a synthesis (combination) reaction? Provide an example.
Two or more substances combine to form a new substance
General Form: A + B -> AB
Example: 2H₂ + O₂ -> 2H₂O
Q: What is a double displacement reaction, and what is its general form?
Two compounds exchange elements to form new compounds.
General Form: AB + CD -> CB + AD
Example: AgNO₃ + NaCl -> AgCl NaNO₃
Q: What is the difference between a coefficient and a subscript in a chemical equation?
Coefficient: A number placed before a compound to balance the equation (e.g., 2H₂O).
Subscript: A small number within a formula that indicates the number of atoms in a molecule (e.g., H₂O).
Q: Why must chemical equations be balanced?
A: Due to the law of conservation of mass, the total number of atoms in reactants must equal the total number in products.
What is a precipitate?
A precipitate is an insoluble solid that forms when two solutions react in a chemical reaction. It settles out of the solution as a solid.
Q: What is an acid-base reaction, and what is its general form?
A: A reaction between an acid and a base that produces a salt and water.
General Form:
Acid (HA) + Base (BOH) → Salt (BA) + H₂O
Example: HCl + NaOH -> NaCl + H₂O
Q: What is a combustion reaction, and what is its general form?
A reaction where a substance reacts with oxygen, often producing heat and light.
General Form:
Hydrocarbon + O₂ -> CO₂ + H₂O+ energy
Example: CH₄ + 2O₂ -> CO₂ + 2H₂O
Q: What is a redox reaction, and what is its general form?
A: A reaction where one species is oxidized (loses electrons) and another is reduced (gains electrons).
Oxidation Is Loss (of electrons)
Reduction Is Gain (of electrons)
Oxidation: A -> A⁺ + e⁻
Reduction B + e⁻ -> B⁻
Example: Zn + Cu²⁺ -> Zn²⁺ + Cu
