1e-Chemical formulae, equations and calculations Flashcards

1
Q

Question: What is a word equation?

A

Answer: A word equation shows the reactants and products of a chemical reaction using their names. Example: Hydrogen + Oxygen → Water

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2
Q

Question: What is a balanced chemical equation?

A

Answer: A balanced equation shows the number of atoms of each element is the same on both sides. Example: 2H₂ + O₂ → 2H₂O

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3
Q

Question: Why are state symbols used in equations?

A

Answer: State symbols show the physical state of substances: (s) solid, (l) liquid, (g) gas, (aq) aqueous.

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4
Q

Question: How do you calculate relative formula mass (Mr)?

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Answer: Mr is the sum of the relative atomic masses (Ar) of all atoms in a formula. Example: Mr of H₂O = (2 × 1) + 16 = 18

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5
Q

Question: What is a mole (mol)?

A

Answer: A mole is the unit of the amount of substance, containing 6.022 × 10²³ particles (Avogadro’s number).

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6
Q

Question: How do you calculate the number of moles?

A

Answer: Moles = Mass / Mr

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7
Q

Question: How do you calculate the mass of a substance?

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Answer: Mass = Moles × Mr

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8
Q

Question: What is percentage yield, and how is it calculated?

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Answer: Percentage yield compares the actual and theoretical yield:Percentage yield = (Actual yield / Theoretical yield) × 100

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9
Q

Question: What is an empirical formula?

A

Answer: The simplest ratio of atoms of each element in a compound.

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10
Q

Question: What is a molecular formula?

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Answer: The actual number of atoms of each element in a compound.

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11
Q

Question: How do you calculate the empirical formula from experimental data?

A

Answer:

Find the mass of each element.

Calculate the moles of each element (Mass / Ar).

Divide by the smallest number of moles.

Write the ratio as the empirical formula.

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12
Q

Question: How do you determine the formula of a metal oxide by combustion?

A

Answer: Example: Magnesium oxide
Weigh magnesium before combustion.

Burn magnesium in air.

Weigh the magnesium oxide formed.

Use the mass difference to calculate the oxygen mass and determine the formula.

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13
Q

Question: How do you determine the formula of copper(II) oxide by reduction?

A

Answer:

Weigh copper(II) oxide before heating.

Heat with hydrogen to remove oxygen.

Weigh the remaining copper.

Calculate the ratio of copper to oxygen to find the formula.

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14
Q
A
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