P1: Topic3

• What does the pH scale indicate?

  • Measures how acidic or alkaline a substance is
  • pH from 0 to 6 is acidic
  • pH of 7 is neutral (usually water)
  • pH from 8 to 14 is alkaline
• What are alkalis defined as?


  Alkalis are soluble bases.
• What happens when acids and alkalis dissolve in water?


  They split up into ions.
• What ions does hydrochloric acid dissociate into?

  Hydrochloric acid dissociates into $H^+$ ions and $Cl^−$ ions.
• What is the significance of $H^+$ ions in acids?


  All acids produce $H^+$ ions when they dissolve.
• What ions do alkalis dissociate into?


  Alkalis dissociate into hydroxide ions $OH^−$.
• What is the process called when acids and alkalis split into ions?


  This process is called dissociation.
• How do strong and weak acids differ in terms of dissociation?

  • Strong acids completely dissociate into ions.
  • Weak acids only partially dissociate into ions.
• What does it mean for a weak acid to be reversible?


  It can change between being dissociated and remaining as molecules.
• What does a neutral pH indicate about $[H^+]$ and $[OH^-]$ concentrations?


  A neutral pH indicates equal concentrations of $H^+$ and $OH^−$ ions.
• What is the difference between concentrated and dilute solutions?

  • Concentrated: High amount of solute in a small volume of solvent.
  • Dilute: Low amount of solute in a large volume of solvent.
• Can a concentrated weak acid have a higher pH than a dilute strong acid?

  Yes, a concentrated weak acid can have a higher pH than a dilute strong acid.
• What are some common acids and their formulas?

  • Hydrochloric acid: HCl
  • Nitric acid: HNO₃
  • Sulfuric acid: H₂SO₄
• What are some common alkalis and their formulas?

  • Sodium hydroxide: NaOH
  • Potassium hydroxide: KOH
  • Calcium hydroxide: Ca(OH)₂
• How can we test if a substance is an acid or an alkali?


  We can use indicators.
• What are the four main indicators used to test acids and alkalis?

  • Methyl orange
  • Phenolphthalein
  • Red litmus paper
  • Blue litmus paper
• What color does methyl orange turn in an acid?

  Methyl orange turns red in an acid.
• What color does phenolphthalein turn in an alkali?


  Phenolphthalein turns bright pink in an alkali.
• What happens to red litmus paper in an acid?


  Red litmus paper stays red in an acid.
• What happens to blue litmus paper in an acid?


  Blue litmus paper turns red in an acid.
• How can we test for hydrogen gas?


  By holding a lit splint over the sample to hear a squeaky pop.
• How can we test for carbon dioxide?


  By bubbling the gas through lime water to see if it goes cloudy.
• How can we test for oxygen gas?


  By holding a glowing splint over it to see if it relights.
• What happens when an acid and a base react together?

  They neutralize each other, resulting in a pH of 7.
• What is the chemical formula for water?


  Water is represented as H₂O.
• What are the products when an acid reacts with a metal oxide or hydroxide?


  • Salt
  • Water
• What are the products when an acid reacts with a metal?

  • Salt
  • Hydrogen gas
• What are the products when an acid reacts with a metal carbonate?


  • Salt
  • Water
  • Carbon dioxide
• What is a salt in the context of acid-base reactions?

  A salt is the product formed when acids and bases react.
• How is sodium chloride formed from hydrochloric acid and sodium hydroxide?

  Sodium chloride is formed when $H^+$ ions from the acid combine with $OH^−$ ions from the alkali.
• What are the solubility rules for salts?

  • All nitrates are soluble.
  • Most chlorides are soluble except silver and lead chlorides.
  • Most sulfates are soluble except lead sulfate, barium sulfate, and calcium sulfate.
  • Most carbonates and hydroxides are insoluble.
• What is copper sulfate and how is it created?


  Copper sulfate is a salt created by reacting copper oxide with sulfuric acid.
• Why is excess copper oxide added when creating copper sulfate?


  Excess copper oxide ensures all sulfuric acid reacts completely.
• What is the purpose of filtration in the copper sulfate reaction?

  Filtration removes unreacted copper oxide from the solution.
• What is the process of crystallization in the context of copper sulfate?


  • Used to obtain pure copper sulfate crystals.
  • Results in bright blue crystals.
• What is the symbol equation for the reaction between copper oxide and sulfuric acid?


  The symbol equation is $CuO +$$H_2SO_4 \rightarrow CuSO_4 +$$H_2O$.
• What is the purpose of a titration?

  • To control the exact amount of reactant added.
  • Used when both reactants are soluble.
• What equipment is primarily used in a titration?


  A burette is primarily used in a titration.
• What is the role of the indicator in a titration?


  The indicator shows when the reactants are fully reacted.
• What happens after performing several titrations with an indicator?

  • You can memorize the number of drops needed.
  • You can perform the titration without the indicator.