Chapter 4: Changes in Matter EST Flashcards

(16 cards)

1
Q

fWhat is stoichiometry?

A

The calculation of quantities in a chemical reaction using balanced equations.

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2
Q

In a balanced chemical equation, what do the coefficients represent?

A

The number of moles of each substance.

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3
Q

In the reaction 2 H₂ + O₂ → 2 H₂O, how many moles of O₂ are needed to react with 6 moles of H₂?

A

6 ÷ 2 = 3 mol O₂

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4
Q

How many grams of carbon are needed for 6 mol Fe₂O₃? (Fe₂O₃ + 3C → 2Fe + 3CO)

A

6 mol Fe₂O₃ × (3 mol C / 1 mol Fe₂O₃) × 12 g/mol = 216 g

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5
Q

If 32 g of CH₄ reacts and the reaction releases 686 kJ per mol, how much energy is released?

A

Molar mass CH₄ = 16 g/mol → 32 g = 2 mol → Energy = 2 × 686 = 1372 kJ

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6
Q

What is an endothermic reaction?

A

A chemical reaction that absorbs energy (heat) from the environment.

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7
Q

What is an exothermic reaction?

A

A chemical reaction that releases energy (heat) to the environment.

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8
Q

On an energy diagram, where is the energy for an endothermic reaction?

A

Products have more energy than reactants (energy is absorbed).

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9
Q

On an energy diagram, where is the energy for an exothermic reaction?

A

Products have less energy than reactants (energy is released).

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10
Q

What is oxidation?

A

A chemical change involving oxygen (or a similar substance) bonding to another substance.

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11
Q

What are some examples of oxidation?

A

Rusting metal, browning apples, burning wood.

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12
Q

How can oxidation be slowed down?

A

Use preservatives, paint, or coat metals.

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13
Q

What is nuclear transformation?

A

A change in the nucleus of an atom that creates a new atom and releases radiation.

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14
Q

What are the 3 types of radiation?

A
  • Alpha (α): +2 charge, stopped by paper
  • Beta (β): -1 charge, stopped by aluminum
  • Gamma (γ): no charge, stopped by concrete
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15
Q

What is nuclear fission?

A

Splitting of a heavy nucleus into smaller parts + lots of energy (ex: nuclear reactors).

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16
Q

What is nuclear fusion?

A

Small nuclei combine to form a larger nucleus (ex: stars, sun). Happens at super high temps.