2.3States of Matter
Solutions — EST 2 Chemistry Revision Notes & Topical Questions
5 min read 8 parts Lesson 3 of 3 1 quiz
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.
Lesson summary
Solutions EST Chemistry notes: Calculate concentration in several units.Molarity uses litres of solution; molality uses kilograms of solvent.Molality does not change with temperature; molarity does slightly.Dilution adds solvent only, so moles of solute stay the same.Concentrated…
- Find the molarity of 11.7 g NaCl in 500 mL of solution
- What volume of 2.0 M HCl makes 500 mL of 0.50 M?
- Solutions EST Chemistry: what to do next
- Molarity (M)
- Molality (m)
- Percent by mass
Section 1 of 8Solutions
1
Always convert mL to L for molarity.
2
Add acid to water, not water to acid, when diluting.
3
Molality is used for colligative properties.
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Percent by mass is common in commercial products.
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Units must be stated with the number.
Section 2 of 8Process & sequence
1
Find moles of solute from its mass.
2
Convert solution volume to litres.
3
Molarity = moles ÷ litres.
4
To dilute, keep moles constant: M1V1 = M2V2.
5
Prepare solutions with a volumetric flask filled to the mark.
Making a solutionwrite these steps in this order; each step is a marking point.
- Weigh solute
- Find moles
- Dissolve
- Make up to volume
- Calculate molarity
Section 3 of 8Compare
| Unit | Formula |
|---|---|
| Percent by mass | msolute/msolution × 100 |
| Percent by volume | Vsolute/Vsolution × 100 |
| Molarity | mol solute / L solution |
| Molality | mol solute / kg solvent |
| Mole fraction | nA / ntotal |
Section 4 of 8Worked examples
1Find the molarity of 11.7 g NaCl in 500 mL of solution.
- 11.7 ÷ 58.44 = 0.200 mol; 0.200 ÷ 0.500 L = 0.400 M.
2What volume of 2.0 M HCl makes 500 mL of 0.50 M?
- V1 = 0.50 × 500 ÷ 2.0 = 125 mL.
Section 5 of 8Keep going
Solutions EST Chemistry: what to do next
These Solutions EST Chemistry notes covered the key ideas, worked examples and exam technique for this topic. Check your Solutions EST Chemistry understanding with the practice questions below, then reread any Solutions EST Chemistry point you were unsure about before moving on.
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Previous lesson: 2.2 Liquids and solids
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Next lesson: 3.1 Acids and bases
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Course: EST 2 Chemistry — all units
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Official syllabus: OpenStax free science textbooks
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
Concentration · Molarity (M) · Molality (m) · Percent by mass · Mole fraction · Dilution
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.
Marked practiceQuizzes for this lesson
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