Reaction Rate: Factors, Enzymes, and Catalysts

• The rate of a reaction indicates how quickly or slowly it progresses which is important for chemists to predict the time needed for product formation.
• The rate of a reaction is quantified as the measure of change occurring over a specific period.
• The rate of reaction is determined by the alteration in the quantity of reactant or product per unit of time.

Factors Affecting Reaction Rate

• A catalyst accelerates a chemical reaction without being consumed or altered in the process.
• Higher temperatures increase reaction rates.
• Increased concentration quickens the reaction speed.
• Smaller particle sizes increase the reaction rate.

Enzymes

• Enzymes function as biological catalysts found in living organisms.
• Potatoes contain an enzyme that speeds up the breakdown of hydrogen peroxide.

Catalysts

• Elephant's toothpaste is an example of a catalyst.
• Adding a catalyst or enzyme accelerates the rate of a chemical reaction.

Catalyst Experiment

• Add 10cm3 of hydrogen peroxide to 4 boiling tubes.
• Add the same amount of each catalyst to different boiling tubes.
• Observe and record the production of oxygen gas.
• Compile results in a table.
• Catalysts speed up reactions without producing more product.

Calculating Average Chemical Reaction Rate

• The formula to calculate the average rate of a chemical reaction is: Rate = ΔQuantity / ΔTime.
• The units for rate calculation are cm3 s-1.

Monitoring Chemical Reactions

• Gas syringe: Collects the volume of gas released over time to monitor a chemical reaction.
• Measuring cylinder: Inverted while full of water to capture and measure released gas volume.
• Mass loss: Method monitors reactions by measuring the decrease in mass due to gas release, example: calcium carbonate and hydrochloric acid reaction releasing CO2.

Interpreting Graphs

• Steeper curve: Indicates a faster reaction rate.
• Less steep slope: Indicates reaction rate is slowing as reactants are used up.
• Horizontal line: Indicates the reaction has stopped.

Signs of a Chemical Reaction

• Color change.
• Temperature change.
• Gas given off.
• Formation of a precipitate.

Testing for Gases

• Carbon dioxide turns limewater milky or cloudy.
• Oxygen causes a glowing splint to relight.
• Hydrogen produces a squeaky pop sound when a lit splint is held in the test tube.

Acids and Bases

Acids at Home and in Laboratories

• Labs: Hydrochloric acid, sulfuric acid, and nitric acid are common laboratory acids.
• Home: Fizzy drinks, vinegar, and fruit juice contain acids.

Alkalis at Home and in Laboratories

• Labs: Sodium hydroxide, potassium hydroxide, and ammonia are common laboratory alkalis.
• Home: Oven cleaner, baking soda, and drain unblocker are alkaline substances.

pH Scale

• Acids have a pH under 7.
• Neutral substances have a pH of 7.
• Alkalis have a pH over 7.
• Acid can cause tooth erosion and cancer growth.

Metal Oxides

• Soluble metal oxides produce alkaline solutions.
• Soluble non-metal oxides produce acidic solutions.
• Insoluble oxides do not affect the pH of water.

Neutralization Reactions

• Neutralization is when an acid reacts with a base (alkali) to form water and a salt.
• The pH of a neutralization reaction is 7.
• Acids contain hydrogen ions (H+), alkalis contain hydroxide ions (OH-), which combine to form water (H2O).

Salts

• Hydrochloric acid forms chloride salts.
• Nitric acid forms nitrate salts.
• Sulfuric acid forms sulfate salts.

Bases Composition

• Bases are metal oxides (like copper oxide), metal carbonates (like calcium carbonate) and metal hydroxides (like sodium hydroxide), and ammonia.
• Insoluble bases dissolve in water, and are called alkalis.

Reaction Example

• Nitric acid + sodium hydroxide yields sodium nitrate + water.
• Acid + alkali yields salt + water.
• A bee sting (acid) can be treated with baking soda (alkali).
• Adding an acid to an alkali increases the acid's pH and decreases the alkali's pH, moving both towards 7.

Titration

• Titration is used to determine accurate volumes in a neutralisation reactions
• Essential for precise volume determination in neutralization reactions.

Titration Techniques

• Stand up.
• Safety glasses on.
• Swirl the flask to detect color change.
• Filter funnel removed from the top of the burette.
• Always take a rough titre but never include it in your average result.

Calculating Average Titre

• Average titre = (24.6 + 24.7) / 2 = 24.65cm³.

Naming Salts: Part 1 & 2

• Sodium hydroxide = Sodium salt
• Potassium oxide = Potassium salt
• Calcium carbonate = Calcium salt
• Ammonia solution = Ammonium salt
• Magnesium = Magnesium salt
• Hydrochloric acid = chloride salt
• Sulfuric acid = sulfate salt
• Nitric acid = nitrate salt
• Phosphoric acid = phosphate salt