Making useful chemicals

"What is the general reaction of acids with metal carbonates?"

"Acid + metal carbonate → salt + water + carbon dioxide."

"What is the general reaction of acids with metals?"

"Acid + metal → salt + hydrogen."

"How are salts named?"

"First part from the metal or base; second part from the acid used (HCl → chloride, HNO₃ → nitrate, H₂SO₄ → sulfate)."

"How do you prepare an insoluble salt?"

"1. Mix two solutions to form the salt. 2. Filter to collect the insoluble salt. 3. Wash with distilled water. 4. Dry on filter paper or in an oven."

"How do you prepare a soluble salt from an insoluble base?"

"1. Add excess base to acid. 2. Filter off unreacted base. 3. Evaporate solution in a water bath. 4. Leave crystals to form."

"How do you prepare a soluble salt from a soluble base?"

"1. Use titration to find exact acid-base volumes. 2. React exact amounts. 3. Evaporate water. 4. Leave crystals of salt."

"What must happen to charges when writing ionic compound formulae?"

"Charges of positive and negative ions must cancel out to form a neutral compound."

"What are the common charges of ions from groups 1

2, 3, 5, 6, and 7?","Group 1 = +1, Group 2 = +2, Group 3 = +3, Group 5 = -3, Group 6 = -2, Group 7 = -1."

"What ions do acids form?"

"HCl → Cl⁻, HNO₃ → NO₃⁻, H₂SO₄ → SO₄²⁻."

"What ions do acids and alkalis release in solution?"

"Acids release H⁺ ions; alkalis release OH⁻ ions."

"What does the pH scale measure?"

"The acidity or alkalinity of a solution (0-14). pH < 7 = acidic, pH = 7 = neutral, pH > 7 = alkaline."

"How can pH be measured?"

"With universal indicator or a pH probe."

"What is a strong acid?"

"An acid that fully ionises in aqueous solution (e.g. hydrochloric, nitric, sulfuric)."

"What is a weak acid?"

"An acid that partially ionises in aqueous solution (e.g. ethanoic, citric, carbonic)."

"What is the difference between strong/weak and concentrated/dilute acids?"

"Strong/weak = degree of ionisation. Concentrated/dilute = amount of substance per volume."

"How does hydrogen ion concentration affect pH?"

"As [H⁺] increases by a factor of 10, pH decreases by 1."

"What happens to OH⁻ and H⁺ concentrations at different pHs?"

"Neutral: [H⁺] = [OH⁻]. Acidic: [H⁺] > [OH⁻]. Alkaline: [OH⁻] > [H⁺]."

"What factors increase rate of reaction?"

"Increasing temperature, concentration, pressure, or surface area."

"Why does increasing temperature increase reaction rate?"

"Particles move faster, collide more often and with more energy."

"Why does increasing concentration or pressure increase reaction rate?"

"More particles in a given volume → higher collision frequency."

"Why does increasing surface area increase reaction rate?"

"More exposed surfaces → more frequent collisions."

"What is a catalyst?"

"A substance that speeds up a reaction without being used up or changed."

"How do catalysts work?"

"They provide an alternative pathway with lower activation energy."

"How can rate of reaction be measured in gas-producing reactions?"

"By measuring gas volume with a syringe or over water, or by mass loss on a balance."

"What is shown by the gradient of a concentration-time graph?"

"The rate of reaction (steeper = faster)."

"How do rate-condition graphs look?"

"Straight line through origin = directly proportional. Horizontal line = no effect. Curved line = not directly proportional."

"What equations are used to calculate rate of reaction?"

"Rate = amount of reactant used ÷ time OR Rate = amount of product formed ÷ time."

"What units can rate of reaction have?"

"g/s, cm³/s, or mol/s."

"What do rate graphs show about reaction speed?"

"Fastest at the start (steepest slope); slows as reactants are used up; stops when line flattens."

"What is the role of enzymes?"

"They are biological catalysts for processes like DNA replication, protein synthesis, digestion, and in industry (e.g. fermentation)."

"What is a reversible reaction?"

"A reaction where products can react to reform reactants (shown with ⇌ symbol)."

"What is dynamic equilibrium?"

"When forward and reverse reactions occur at the same rate in a closed system; concentrations stay constant."

"How does concentration affect equilibrium position?"

"Increase reactant concentration → shifts right (more product). Increase product concentration → shifts left (more reactant)."

"How does temperature affect equilibrium?"

"Increase T → equilibrium shifts in endothermic direction. Decrease T → shifts in exothermic direction."

"How does pressure affect equilibrium?"

"Increase pressure → shifts to side with fewer moles of gas. Decrease pressure → shifts to side with more moles."

"How do catalysts affect equilibrium?"

"They increase the rate of reaching equilibrium but do not change yield."

"What are the disadvantages of very high temperature and pressure in industry?"

"Expensive, dangerous, and may lower yield if conditions don't favour the forward reaction."

"Why are nitrogen

phosphorus and potassium compounds important?","They are fertilisers that improve crop yield; plants absorb them as soluble salts."

"What is the Haber process used for?"

"To manufacture ammonia for fertilisers."

"What are the raw materials for the Haber process?"

"Nitrogen (from air) and hydrogen (from natural gas or steam)."

"What are the conditions of the Haber process?"

"Iron catalyst, 450 °C, 200 atm."

"Why are compromise conditions used in the Haber process?"

"Balance between high yield (favoured by low T, high P) and fast rate (favoured by high T, high P) while keeping costs safe and practical."

"What happens to unreacted nitrogen and hydrogen in the Haber process?"

"They are recycled back into the reactor."

"What is atom economy?"

"A measure of how much of the reactants end up in the desired product."

"What is the formula for atom economy?"

"Atom economy = (Mr of desired product ÷ total Mr of reactants) × 100."

"Why is atom economy important?"

"For sustainability and cost-efficiency - high atom economy means less waste."

"What factors influence choice of reaction pathway?"

"Atom economy, yield, rate, equilibrium position, usefulness of by-products, sustainability."

"What are NPK fertilisers?"

"Formulations containing nitrogen, phosphorus, and potassium in appropriate percentages."

"How can phosphate rock be made into fertiliser?"

"By treating it with nitric acid or sulfuric acid to produce soluble salts."

"How is ammonium sulfate made in the lab?"

"Small scale: titration of ammonia solution and sulfuric acid, then crystallisation."

"How is ammonium sulfate made in industry?"

"Large scale: multi-step process using natural gas, air, water (for ammonia) and sulfur, air, water (for sulfuric acid), then reacting and crystallising."