Chapter 4: Changes in Matter EST Flashcards
(16 cards)
fWhat is stoichiometry?
The calculation of quantities in a chemical reaction using balanced equations.
In a balanced chemical equation, what do the coefficients represent?
The number of moles of each substance.
In the reaction 2 H₂ + O₂ → 2 H₂O, how many moles of O₂ are needed to react with 6 moles of H₂?
6 ÷ 2 = 3 mol O₂
How many grams of carbon are needed for 6 mol Fe₂O₃? (Fe₂O₃ + 3C → 2Fe + 3CO)
6 mol Fe₂O₃ × (3 mol C / 1 mol Fe₂O₃) × 12 g/mol = 216 g
If 32 g of CH₄ reacts and the reaction releases 686 kJ per mol, how much energy is released?
Molar mass CH₄ = 16 g/mol → 32 g = 2 mol → Energy = 2 × 686 = 1372 kJ
What is an endothermic reaction?
A chemical reaction that absorbs energy (heat) from the environment.
What is an exothermic reaction?
A chemical reaction that releases energy (heat) to the environment.
On an energy diagram, where is the energy for an endothermic reaction?
Products have more energy than reactants (energy is absorbed).
On an energy diagram, where is the energy for an exothermic reaction?
Products have less energy than reactants (energy is released).
What is oxidation?
A chemical change involving oxygen (or a similar substance) bonding to another substance.
What are some examples of oxidation?
Rusting metal, browning apples, burning wood.
How can oxidation be slowed down?
Use preservatives, paint, or coat metals.
What is nuclear transformation?
A change in the nucleus of an atom that creates a new atom and releases radiation.
What are the 3 types of radiation?
- Alpha (α): +2 charge, stopped by paper
- Beta (β): -1 charge, stopped by aluminum
- Gamma (γ): no charge, stopped by concrete
What is nuclear fission?
Splitting of a heavy nucleus into smaller parts + lots of energy (ex: nuclear reactors).
What is nuclear fusion?
Small nuclei combine to form a larger nucleus (ex: stars, sun). Happens at super high temps.