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3.4Reaction Types

Precipitation and other reactions — EST 2 Chemistry Revision Notes & Topical Questions

5 min read 8 parts Lesson 4 of 4 1 quiz

📚 EST 2 Chemistry Hub / Topical Revision
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Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
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Lesson summary

Precipitation and other reactions EST Chemistry notes: Classify reactions by type.A double replacement proceeds if it forms a precipitate, gas or water.A metal replaces another only if it is higher in the activity series.Complete combustion of hydrocarbons gives CO2 and H2O; inco…

  • Halogens also have an activity series
  • Write the net ionic equation for BaCl2(aq) + Na2SO4(aq)
  • Precipitation and other reactions EST Chemistry: what to do next
  • Spectator ion
  • Decomposition
  • Single replacement

Section 1 of 8Precipitation and other reactions

Essential knowledge
Nitrates are always soluble — useful when choosing reagents.
Halogens also have an activity series
F2 > Cl2 > Br2 > I2.
Gold and platinum are very unreactive.
Na, K react vigorously with water.
Neutralization is a type of double replacement.

Section 2 of 8Process & sequence

1
Write the ions present in both solutions.
2
Swap partners to find possible products.
3
Use solubility rules to spot the precipitate.
4
Write the complete ionic equation.
5
Cancel spectator ions to get the net ionic equation.

Predicting a precipitatewrite these steps in this order; each step is a marking point.

  1. List ions
  2. Swap partners
  3. Check solubility
  4. Ionic equation
  5. Cancel spectators

Section 3 of 8Compare

Solubility rules (water)
Usually solubleExceptions
Group 1 and NH4+ saltsNone
Nitrates, acetatesNone
Chlorides, bromides, iodidesAg+, Pb2+, Hg22+
SulfatesBa2+, Pb2+, Ca2+, Sr2+
Usually insoluble
IonExceptions
Carbonates, phosphatesGroup 1, NH4+
HydroxidesGroup 1, Ba2+, (Ca2+ slightly)
SulfidesGroup 1, 2, NH4+
Reaction types
TypePatternExample
SynthesisA + B → AB2Mg + O2 → 2MgO
DecompositionAB → A + BCaCO3 → CaO + CO2
Single replacementA + BC → AC + BZn + 2HCl → ZnCl2 + H2
Double replacementAB + CD → AD + CBAgNO3 + NaCl → AgCl + NaNO3
CombustionCxHy + O2 → CO2 + H2OCH4 + 2O2 → CO2 + 2H2O

Section 4 of 8Worked examples

  1. Write the net ionic equation for BaCl2(aq) + Na2SO4(aq).

Section 5 of 8Keep going

Precipitation and other reactions EST Chemistry: what to do next

These Precipitation and other reactions EST Chemistry notes covered the key ideas, worked examples and exam technique for this topic. Check your Precipitation and other reactions EST Chemistry understanding with the practice questions below, then reread any Precipitation and other reactions EST Chemistry point you were unsure about before moving on.

1
Practice: Precipitation and other reactions EST Chemistry practice questions
2
Previous lesson: 3.3 Redox & Electrochemistry — EST II Notes
3
Next lesson: 4.1 The mole
4
Course: EST 2 Chemistry — all units
5
Official syllabus: OpenStax free science textbooks

Precipitation and other reactions EST Chemistry revision notes

Section 6 of 8Key terms

Section 7 of 8Command terms

Command terms
Identify / Describe (FRQ)
A short, specific statement; describing requires relevant characteristics, not a single word.
Explain / Justify (FRQ)
Give the cause-and-effect reasoning or evidence; a restated fact does not score.
Calculate
Show setup, substitution and the answer with units.
Predict
State the expected outcome; add a reason only if asked to justify.
MCQ technique
Read every option; eliminate distractors that are true statements but do not answer the question; watch for NOT/EXCEPT.

Section 8 of 8Exam technique

Keywords the mark scheme looks for in this lesson

Keywords the mark scheme looks for in this lesson
Precipitate · Spectator ion · Net ionic equation · Synthesis · Decomposition · Single replacement · Double replacement · Combustion · Activity series
Learn each definition in the Key words tab exactly; a missing keyword in a definition usually loses the mark.

How to get full marks (examiner guidance)

1
Answer exactly what is asked; extra correct material does not earn credit, and contradictory statements can cancel credit (AP FRQ).
2
Use precise vocabulary (e.g. “active site”, “concentration gradient”, “allele”), never “it/stuff/things”.
3
Show units and working in calculations.
4
In MCQs, predict the answer before reading the options, then eliminate.

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