Chemical equations and stoichiometry
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All 12 Flashcards — Chemical equations and stoichiometry
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Question
What is a balanced chemical equation?
Answer
An equation with the **same number of each kind of atom** on both sides — atoms are conserved.
Question
What is stoichiometry?
Answer
The study of the **whole-number ratios** in which substances react and are formed, read from a balanced equation.
Question
What is a mole ratio?
Answer
The ratio of the **coefficients** in a balanced equation — how many moles of one substance react with or form another.
Question
When balancing, what may you change?
Answer
Only the **coefficients** (the big numbers in front) — **never** a subscript inside a formula.
Question
Why can't you change a subscript to balance?
Answer
Changing a subscript changes the **substance** itself (e.g. H_{2}O → H_{2}O_{2}), so it no longer describes the same reaction.
Question
List the four state symbols.
Answer
**(s)** solid, **(l)** pure liquid, **(g)** gas, **(aq)** aqueous (dissolved in water).
Question
What does (aq) mean?
Answer
**Aqueous** — the substance is **dissolved in water** (different from a pure liquid, (l)).
Question
How do you read a mole ratio from N_{2} + 3 H_{2} → 2 NH_{3}?
Answer
The ratio N_{2} : H_{2} : NH_{3} is **1 : 3 : 2** — 1 mol N_{2} reacts with 3 mol H_{2} to make 2 mol NH_{3}.
Question
Tip for balancing combustion equations?
Answer
Balance **C first, then H, then O last** (oxygen appears in more than one product), then reduce to smallest whole numbers.
Question
Balanced equation for combustion of methane?
Answer
**CH_{4} + 2 O_{2} → CO_{2} + 2 H_{2}O** — smallest whole-number coefficients.
Question
How much CO_{2} forms from 0.5 mol C in C + O_{2} → CO_{2}?
Answer
The C : CO_{2} ratio is 1 : 1, so **0.5 mol** of CO_{2}.
Question
Common balancing mistake?
Answer
Changing a **formula** (subscript) instead of a coefficient, or forgetting the **state symbols** when asked.
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Full study notes for Chemical equations and stoichiometry
Topic 5.1 hub
How much? The amount of chemical change
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