C4 Chemical changes

• What is the pH scale range?

  0 to 14
• What does a lower pH indicate about a solution?

  The lower the pH of a solution, the more acidic it is.
• What does a higher pH indicate about a solution?

  The higher the pH of a solution, the more alkaline it is.
• What is the pH of pure water?

  7
• What is the purpose of an indicator in measuring pH?


  • An indicator changes color depending on the pH level.
  • Wide range indicators gradually change color over a broad pH range.
  • Universal indicator provides a spectrum of colors for different pH values.
• How can pH be measured electronically?

  Using a pH meter with a probe that displays the pH value digitally.
• What is an acid defined as in terms of pH?

  An acid is a substance that forms aqueous solutions with a pH of less than 7.
• What is a base defined as in terms of pH?

  A base is a substance with a pH greater than 7.
• What is an alkali?

  An alkali is a base that dissolves in water to form a solution with a pH greater than 7.
• What is the neutralization reaction between acids and bases?

  • The reaction produces salt and water.
  • The general equation is: Acid + Base → Salt + Water.
  • The resulting solution has a pH of 7.
• What happens to the pH when an acid neutralizes a base?

  The products are neutral, meaning they have a pH of 7.
• What is the role of an indicator in a neutralization reaction?

  An indicator shows when the neutralization reaction is complete.
• How can titrations be used in chemistry?

  Titrations are used to find out how much acid is needed to neutralize a quantity of alkali or vice versa.
• What are the steps involved in performing a titration?

  1. Add a known volume of alkali to a conical flask.
  2. Add a few drops of indicator to the alkali.
  3. Use a burette to add acid to the alkali slowly.
  4. Observe the color change to determine the endpoint.
  5. Record the volume of acid used to neutralize the alkali.
• What is the purpose of a rough titration?

  A rough titration gives an approximate idea of where the solution changes color (the end-point).
• Why is it important to repeat titrations?


  Repeating titrations ensures consistent readings and accuracy in results.
• What is a strong acid?

  A strong acid is one that completely ionizes in water.
• What is a weak acid?

  A weak acid is one that does not fully ionize in solution.
• What is the difference between strong acids and concentrated acids?

  Strong acids ionize completely in water, while concentrated acids have a high amount of acid in a given volume of water.
• Can a dilute solution be a strong acid?

  Yes, a dilute solution can be a strong acid if it ionizes completely.
• How does pH change with increasing acid concentration?

  pH will decrease with increasing acid concentration regardless of whether it's a strong or weak acid.
• What do metal oxides and metal hydroxides react with?

  Metal oxides and metal hydroxides react with acids.
• What are the products of the reaction between an acid and a metal carbonate?

  • Salt
  • Water
  • Carbon Dioxide
• What is the general equation for the reaction between an acid and a metal carbonate?

  Acid + Metal Carbonate → Salt + Water + Carbon Dioxide.
• How do you make soluble salts using an insoluble base?

  1. Choose the right acid and insoluble base.
  2. Warm the dilute acid.
  3. Add the insoluble base until no more reacts.
  4. Filter out the excess solid.
  5. Evaporate some water to crystallize the salt.
• What is the reactivity series?

  The reactivity series ranks metals in order of their reactivity towards other substances.
• How does the position of a metal in the reactivity series affect its reactions with acids?

  The higher a metal is in the reactivity series, the more easily it reacts with acids.
• What is produced when metals react with acids?

  Salt and hydrogen gas are produced when metals react with acids.
• How can the speed of a reaction with an acid be measured?

  The speed of reaction can be indicated by the rate at which hydrogen bubbles are produced.
• What happens to very reactive metals when they react with acids?

  Very reactive metals react explosively with acids.
• How do less reactive metals behave when reacting with acids?

  Less reactive metals react less violently with acids.
• What is the general reaction equation for metals reacting with acids?

  Acid + Metal → Salt + Hydrogen.
• How can the reactivity of metals be investigated?

  By measuring the temperature change of the reaction with an acid or water over a set time period.
• What do metals produce when they react with acids?

  Salt and hydrogen gas
• How is the speed of a reaction with acids indicated?

  By the rate at which bubbles of hydrogen are given off
• What is the relationship between metal reactivity and the speed of reaction with acids?

  The more reactive the metal, the faster the reaction will go
• Which metals react explosively with acids?

  Potassium, sodium, lithium, and calcium
• How do less reactive metals like magnesium, zinc, and iron react with acids?

  They react less violently compared to more reactive metals
• Will copper react with cold, dilute acids?

  No, copper won't react with cold, dilute acids
• What happens when magnesium reacts with dilute acids?

  Magnesium reacts strongly with dilute acids