ما هي معادلة البناء الضوئي الكيميائية الموزونة؟ What is the balanced equation for photosynthesis?

المعادلة الموزونة هي: 6CO₂ + 6H₂O ➔ C₆H₁₂O₆ + 6O₂ (ستة جزيئات ثاني أكسيد الكربون + ستة جزيئات ماء في وجود طاقة الضوء وصبغة الكلوروفيل تعطي جزيء جلوكوز وستة جزيئات أكسجين). وتتطلب العملية تفاعلات ضوئية لإنتاج ATP و NADPH يعقبها تفاعلات لاضوئية لتثبيت الكربون. [الصيغة الرمزية الموزونة: 6CO₂ + 6H₂O ➔ C₆H₁₂O₆ + 6O₂]

2.2.2Inorganic Chemistry: Part 1

Acids, Alkalis and Neutralisation

5 min read 6 parts Lesson 9 of 20 1 quiz

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Section 1 of 6Acids, alkalis and the pH scale

Acids, alkalis and the pH scale

Acids

Acids substances that dissolve in water to produce hydrogen ions, H⁺(aq). (pH less than 7).

Bases

Bases substances that neutralise acids to form a salt and water (metal oxides and metal hydroxides).

Alkalis

Alkalis soluble bases that dissolve in water to produce hydroxide ions, OH^-(aq). (pH greater than 7).

Indicators and pH

Universal Indicatorred (strong acid), yellow/green (weak acid), green (neutral, pH 7), blue (weak alkali), purple (strong alkali).
Litmusred in acid, blue in alkali.
Methyl orangered in acid, yellow in alkali.
Phenolphthaleincolourless in acid, bright pink in alkali.

Neutralisation ionic equation

H⁺(aq) + OH^-(aq) → H_2O(l)

Section 2 of 6Reactions of acids

Reactants	Products	Example Equation
Acid + Metal	Salt + Hydrogen	Mg + 2HCl → MgCl₂ + H₂
Acid + Metal Oxide	Salt + Water	CuO + H_2SO₄ → CuSO₄ + H_2O
Acid + Metal Hydroxide	Salt + Water	NaOH + HCl → NaCl + H_2O
Acid + Metal Carbonate	Salt + Water + Carbon Dioxide	CaCO₃ + 2HCl → CaCl₂ + H_2O + CO₂

Section 3 of 6Strong vs weak acids

Strong vs weak acids

Strong acids

Strong acids fully dissociate/ionise in aqueous solution:

HCl(aq) → H⁺(aq) + Cl^-(aq)

Examples: hydrochloric acid (HCl), sulfuric acid (H_2SO₄), nitric acid (HNO₃).

Weak acids

Weak acids only partially dissociate/ionise in aqueous solution (reversible reaction at equilibrium):

CH_3COOH(aq) ⇌ CH_3COO^-(aq) + H⁺(aq)

Examples: ethanoic acid, citric acid, carbonic acid.

Strength vs concentration

Strength refers to the degree of ionisation of acid molecules in water.
Concentration refers to the amount of acid dissolved in a given volume of solution (mol dm^-3 or g dm^-3).

Section 4 of 6Key terms

Term	Meaning
Acid	A substance that releases H⁺ ions when dissolved in water.
Alkali	A soluble base that releases OH^- ions in water.
Neutralisation	The reaction between H⁺ and OH^- ions to produce neutral water (H_2O).
Strong acid	An acid that completely dissociates into ions in aqueous solution.
Weak acid	An acid that only partially dissociates into ions in aqueous solution.

Section 5 of 6Syllabus checklist

Preparation of copper sulfate crystals from copper(II) oxide and sulfuric acid:
- 1. Warm sulfuric acid gently in a beaker over a water bath.
- 2.
  - Add insoluble copper(II) oxide powder in excess, stirring until no more dissolves (ensures all acid is neutralised).
- 3. Filter the warm mixture to remove the unreacted excess black copper oxide residue.
- 4. Heat the clear blue filtrate in an evaporating basin until the crystallisation point is reached.
- 5. Leave to cool slowly, filter the crystals, and pat dry with filter paper.

Section 6 of 6Exam technique

Avoid these mistakes

Confusing strong and concentrated — a strong acid fully ionises regardless of concentration; a concentrated acid simply contains many moles per unit volume.

Heating copper sulfate crystals to complete dryness — this produces anhydrous white powder instead of hydrated blue crystals; always crystallise by cooling.