Quantitative Chemistry Flashcards

(18 cards)

1
Q

Q: What is the Law of Conservation of Mass?

A

A: Mass is neither created nor destroyed in a chemical reaction. The mass of the products equals the mass of the reactants in a closed system.

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2
Q

Q: What is the Relative Formula Mass (Mr)?

A

A: Mr is the sum of the relative atomic masses (Ar) of all atoms in a formula.

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3
Q

Q: How do you calculate the Mr of a compound like H₂O?

A

A: Mr of H₂O = (2 × Ar of H) + (1 × Ar of O) = (2 × 1) + (16) = 18

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4
Q

Q: What is a mole in chemistry?

A

A: 1 mole = 6.02 × 10²³ particles (Avogadro’s number). It’s the amount of a substance that contains the same number of particles as there are in 12g of carbon-12.

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5
Q

Q: How do you calculate the number of moles?

A

A: Moles = Mass (g) ÷ Relative Formula Mass (Mr)

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6
Q

Q: How do you calculate the mass from moles?

A

A: Mass = Moles × Mr

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7
Q

Q: What is a limiting reactant?

A

A: The reactant that is completely used up first in a reaction, limiting the amount of product formed.

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8
Q

Q: How do you find the limiting reactant?

A

A: Compare the mole ratio of reactants used in the reaction. The one that runs out first is the limiting reactant.

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9
Q

Q: How does a limiting reactant affect the yield of a product?

A

A: The limiting reactant controls how much product is formed. Once it’s used up, the reaction stops.

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10
Q

Q: What happens to mass in an open system during a reaction?

A

A: The mass can change because gases may escape or be absorbed into the system.

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11
Q

Q: What happens to mass in a closed system during a reaction?

A

A: The mass remains the same because no substances can enter or leave the system.

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12
Q

Q: How do you calculate concentration of a solution?

A

A: Concentration (g/dm³) = Mass of solute (g) ÷ Volume of solution (dm³)

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13
Q

Q: What is a balanced chemical equation?

A

A: A chemical equation where the number of atoms of each element is the same on both sides of the equation.

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14
Q

Q: Why is it important to balance chemical equations?

A

A: To satisfy the Law of Conservation of Mass – no atoms are lost or gained.

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15
Q

Q: How do you calculate the theoretical yield?

A

A: Use the limiting reactant to find the amount of product that should be formed in a reaction (based on stoichiometry).

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16
Q

Q: What is the actual yield?

A

A: The actual amount of product obtained from a reaction. It may be lower than the theoretical yield due to factors like incomplete reactions or losses during extraction.

17
Q

Q: What is the percentage yield?

A

A: Percentage yield = (Actual yield ÷ Theoretical yield) × 100

18
Q

Q: How can mass changes be used to identify a reaction type?

A

A: Mass changes can indicate whether a gas has been produced or absorbed during a reaction, revealing whether it’s an exothermic or endothermic reaction.