Reaction Rates
Chemistry is Everywhere
Get out your Calculators!
Under Pressure
Chemmon Sense
100
The rate of a reaction is the amount of a ______ that is consumed or a ______ that is produced per unit time.
reactant, product
100
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).
100
Convert 2 days into minutes.
2 880 minutes
100
What happens to gas pressure when volume decreases and temperature stays constant?
Pressure increases.
100
Why does ice float in water?
Solid water is less dense than liquid water.
200
Why does increasing concentration increase the rate of a reaction?
More particles per volume → more collisions.
200
You cut up your food into smaller pieces before cooking it. Will the food cook faster, slower, or the same, and why?
Faster. Increases surface area → increases rate of heat transfer (or reaction rate).
200
A student burns 22.0 g of propane (C₃H₈).
How many moles of propane are burned?
0.50mol
200
A gas is at 2.0 L and is compressed to 1.0 L (temp constant).
Pressure becomes ___ times bigger.
2
200
Why are alkali metals (Group 1) so reactive?
They have 1 valence electron that is easily lost.
300
A catalyst is added to a reaction. On a Maxwell–Boltzmann (Energy Distribution) graph, what changes?
The activation energy (Ea) is lowered.
300
How do antacid medications (like pepcid) help relieve heartburn?
They neutralize excess stomach acid (acid–base neutralization).
300
A reaction uses up 0.40 mol of reactant in 5.0 minutes.
Calculate the average rate of reaction in mol/s.
0.0013 mol/s
300
Which law describes the relationship between pressure and volume?
Boyle's Law
300
During your Water Flow lab, name 1 possible source of experimental error.
- reading a moving value
- human reaction time
400
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.
400
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
400
A 15.0g piece of hot metal at 150.0°C is placed in 100.0g of water at 20.0°C. The final temperature of the water is 25.0°C. What is the heat absorbed by the water?
2 090J or 2.09kJ
400
A 2.0mol sample of gas occupies 10.0L at 301K.
What is the pressure of the gas?
500kPa
400
Describe point E and state if the graph is illustrating an endothermic or exothermic reaction.
E = ΔH (heat of reaction, enthalpy)
Exothermic
500
For a reaction: Rate = k[A]²[B]
If [A] is doubled and [B] stays constant, the rate changes by what factor?
The rate increases by a factor of 4.
500
Write an equation for the complete combustion of propane in your BBQ (C3H8).
Bonus: Balance the equation.
C3H8 + 5O2 → 3CO2 + 4H2O
500
A 6.40g sample of methane (CH₄) is burned. After 2 minutes, 1.60g remains. Calculate the average rate in mol/s.
0.00250 mol/s
500
A balloon filled with air is placed in a freezer.
Explain what happens to its volume and describe what happens to particle motion using kinetic molecular theory.
Volume decreases
Temperature decreases
Particles move slower
Fewer/less forceful collisions with container walls
Pressure drops (if flexible container, volume decreases)
500
A metal spoon and a wooden spoon are left in a pot of hot soup for a few minutes. Both spoons are at the same temperature, but why does the metal spoon feel hotter to your hand?
- Metal is a better thermal conductor
- Heat transfers faster through metal than wood