Exploring Substances: Acidic, Basic, and Neutral – Formula & Equation Sheet
Essential formulas and equations from Curiosity, tailored for Class 7 in Science.
This one-pager compiles key formulas and equations from the Exploring Substances: Acidic, Basic, and Neutral chapter of Curiosity. Ideal for exam prep, quick reference, and solving time-bound numerical problems accurately.
Key concepts & formulas
Essential formulas, key terms, and important concepts for quick reference and revision.
Formulas
pH = -log[H⁺]
pH indicates the acidity or basicity of a solution, where [H⁺] is the concentration of hydrogen ions (in mol/L). A lower pH value indicates acidity, while a higher value indicates basicity. Useful for determining the nature of a solution.
Neutralization Reaction: Acid + Base → Salt + Water
This general equation represents the neutralization process, yielding a salt and water. Commonly observed in titration experiments in chemistry.
[H⁺] x [OH⁻] = 1 x 10⁻¹⁴
This relationship holds true for aqueous solutions at 25°C, where [H⁺] is hydrogen ion concentration and [OH⁻] is hydroxide ion concentration. It emphasizes the balance in neutral solutions.
Litmus Test: Acid (Red) | Base (Blue)
Indicates the nature of a solution using litmus paper. Red litmus turns blue in basic solutions, and blue litmus turns red in acidic solutions. Quick qualitative assessment.
Lime Water Preparation: Ca(OH)₂ + H₂O
Lime water is prepared by dissolving calcium hydroxide (Ca(OH)₂) in water. It is used to test for carbon dioxide by turning milky when CO₂ is bubbled through it.
pH Indicator Range: 0-14
Measures acidity (0-6) and basicity (8-14); a pH of 7 indicates neutrality. Conceptually important for understanding solution properties.
[OH⁻] = Kw/[H⁺]
Where Kw = 1 x 10⁻¹⁴; useful for calculating hydroxide ion concentration when hydrogen ion concentration is known.
Acids and Bases: HA → H⁺ + A⁻
Denotes the dissociation of an acid (HA) into hydrogen ions (H⁺) and its conjugate base (A⁻). Provides insight into acid strength.
Ksp = [Ca²⁺][OH⁻]²
Specifically for calcium hydroxide, where Ksp is the solubility product constant. Important for understanding solubility in water.
Hydronium Ion Formation: H₂O + H⁺ → H₃O⁺
Describes how water reacts with a proton (H⁺) to form hydronium ion (H₃O⁺), crucial in acidic solutions.
Equations
Ohm’s Law: V = IR
V is voltage (volts), I is current (amperes), and R is resistance (ohms). It defines the relationship between current and voltage in a circuit, useful for electronics.
Total Volume of Solutions: V₁ + V₂ = V_total
Where V₁ and V₂ are volumes of mixed solutions. Useful for understanding concentration changes in mixtures.
Concentration Calculation: C = n/V
Where C is concentration (mol/L), n is number of moles, and V is volume (L). Important for preparing solutions in chemistry.
Dilution Equation: C₁V₁ = C₂V₂
Relates the concentrations and volumes of a concentrated solution (C₁, V₁) and a diluted solution (C₂, V₂). Useful for calculating dilutions.
Law of Conservation of Mass: m_reactants = m_products
Indicates that mass is neither created nor destroyed in a chemical reaction. Essential for balancing chemical equations.
Chemical Reaction Rate: Rate = Δ[reactants]/Δt
Defines the change in concentration of reactants over time (t), important for understanding reaction speeds.
Equilibrium Constant: K_eq = [products]/[reactants]
Represents the ratio of concentrations at equilibrium. Useful for predicting reaction direction.
Reaction Yield: Percent Yield = (Actual Yield/Theoretical Yield) x 100
Compares actual vs. expected product amounts, helping assess experimental efficiency.
Molarity (M) = moles of solute/Liters of solution
Molarity describes the concentration of a solution, important for stoichiometry in chemical reactions.
Combustion Reaction: CₓHᵧ + O₂ → CO₂ + H₂O
General equation for combustion involving hydrocarbons, crucial for understanding energy production in reactions.
