Reaction Rates
The rate of a reaction is the amount of a ______ that is consumed or a ______ that is produced per unit time.
reactant, product
Why does food last longer in the fridge than on the counter?
Lower temperature slows chemical reactions that cause spoilage, bacteria grows slower, particles move slower (fewer collisions).
Convert 2 days into minutes.
2880 minutes.
What happens to gas pressure when volume decreases and temperature stays constant?
Pressure increases.
Why does ice float in water?
Solid water is less dense than liquid water.
List two factors that can increase the rate of a chemical reaction.
Any 2:
- temperature
- concentration
- surface area
- catalyst
Faster, more surface area.
A student burns 22.0 g of propane (C₃H₈).
How many moles of propane are burned?
0.50mol
A gas is at 2.0 L and is compressed to 1.0 L (temp constant).
Pressure becomes ___ times bigger.
2
What products are formed during a classic acid-base (neutralization) reaction?
A salt and water
A reaction stops even though reactants are still present.
Give one possible reason why the reactants are no longer reacting.
Temperature dropped, reactants were separated, pressure changed (for gases), or there wasn’t enough energy for the reaction to continue.
How do antacid medications (like pepcid) help relieve heartburn?
They neutralize excess stomach acid (acid–base neutralization).
A gas has a volume of 4.0 L at 100 kPa.
If the pressure increases to 200 kPa, what is the new volume (temperature constant)?
2.0L
Which law describes the relationship between pressure and volume?
Boyle's Law
In an acid-base titration using phenolphthalein, what we call the point when the solution just changes colour?
The end point.
Rate the following reaction as fast or slow (@ room temperature) and justify your answer:
2KOH(aq) + H2SO4(aq) → 2H2O(l) + K2SO4(aq)
Fast, ionic bond changes (i.e. neutralization) happen quickly.
Explain how the chemical properties of acids make metal containers unsuitable for storing acidic foods (like lemon juice).
Acids react with metals
Corrosion occurs
Metal can dissolve into food
A reaction uses up 0.40 mol of reactant in 5.0 minutes.
Calculate the average rate of reaction in mol/s.
0.0013 × 10 mol/s
What are the units for the ideal gas constant (R)?
kPa•L/mol•K
During your titration lab, name 2 possible sources of experimental error.
- equipment uncertainty
- surpassing the end point
- misreading the burette
- air bubbles in the burette tip
- substance stuck to sides of the flask
- incomplete mixing
If each graph represents a reaction in concentration (mol) vs time (s), at t = 10 s, which of the following graphs shows a reaction rate of 0.875 mol/s?
Graph 2
Write an equation for the complete combustion of propane in your BBQ (C3H8).
Bonus: Balance the equation.
A 7.00g sample of methane gas (CH4) was burned in oxygen. After 1 minute and 49 seconds, 2.00g of methane remained.
Calculate the average rate of combustion of methane gas in mol/s.
0.00285 mol/s
A balloon filled with air is placed in a freezer and then taken out after a few minutes. Name 1 effect you would observe and explain why.
Balloon shrinks - particles move slower
A metal spoon and a wooden spoon are left in a pot of hot soup for a few minutes. You notice that the metal spoon feels much hotter - why?
- Metal is a better thermal conductor
- Heat transfers faster through metal than wood