C6 Ai 2 Flashcards
What is the speed of a reaction called?
Its rate
How can graphs help in understanding reaction rates?
They show how the rate (speed) of a reaction changes
What does a steeper line on a reaction rate graph indicate?
A faster rate of reaction
What happens to the slope of the graph over time as reactants are used up?
The line becomes less steep
What is the effect of changing conditions on reaction rates?
Reaction rates can change when conditions like time change
What does a faster reaction look like on a graph compared to a slower reaction?
It has a steeper line at the beginning and goes flat more quickly
What does line 4 on a reaction graph indicate?
More product is formed due to more reactants at the start
What is collision theory?
An idea that explains reaction rates based on particle collisions
What is the minimum amount of energy needed for a reaction to occur called?
Activation energy
What relationship does collision frequency have with reaction rates?
The more often particles collide, the faster the reaction will happen
Fill in the blank: For particles to react, they have to collide with each other with enough _______.
Energy
What factors can affect the rate of reaction?
- Temperature
- Concentration
- Pressure of a gas
- Surface area
What happens to reaction rates when temperature increases?
Particles move faster and collide more often
What is the effect of increasing concentration on reaction rates?
More particles in the same volume lead to more collisions
What effect does surface area have on reaction rates?
Larger surface area increases reaction rates
What are the four factors that affect the rate of a chemical reaction?
- Temperature
- Concentration of a solution (or pressure of a gas)
- Surface area of a solid
- Whether a catalyst is used
These factors influence how frequently particles collide and the energy involved in the reactions.
How does temperature affect the rate of reaction?
Increasing temperature causes particles to move faster, leading to more frequent collisions with sufficient energy to react.
Higher temperatures increase the kinetic energy of particles, which increases the rate of reaction.
What is collision frequency?
How often the particles collide.
Collision frequency is an important concept as it affects the rate of reaction.
Fill in the blank: A _______ is a substance that speeds up a reaction without being used up in the reaction.
[catalyst]
What effect does increasing the surface area of a solid reactant have on the rate of reaction?
It increases the rate of reaction by making more of the solid’s particles available for collisions.
Smaller pieces of solid have a larger surface area to volume ratio, leading to more frequent collisions with other reactants.
True or False: Catalysts are part of the reaction equation.
False
Catalysts are not consumed in the reaction and do not appear in the reaction equation.
What is the role of enzymes in biological reactions?
Enzymes are biological catalysts that catalyse reactions in living things.
Enzymes lower the activation energy needed for reactions, similar to chemical catalysts.
What happens to the activation energy when a catalyst is used?
The activation energy is lowered.
This allows reactions to occur more easily and quickly.
What is the effect of high concentration on reaction rates?
Higher concentration increases the rate of reaction due to more frequent collisions between reactant particles.
Increased concentration means more particles are present in a given volume.
Fill in the blank: Breaking a solid reactant into smaller pieces increases its _______.
[surface area]
In an experiment with magnesium ribbon and powdered magnesium, which would react faster?
Powdered magnesium
The greater surface area of powdered magnesium allows for more frequent collisions with hydrochloric acid.
What is a reaction profile?
A graphical representation showing the energy changes during a reaction, including activation energy.
Reaction profiles illustrate the difference in activation energy with and without a catalyst.
What happens to reaction rates if the particles collide with enough energy?
The reaction will occur.
Sufficient energy is required for a successful reaction to take place.
What is the first step in measuring rates of reaction?
Measure out a set volume of dilute hydrochloric acid using a measuring cylinder.
What should be done after measuring the hydrochloric acid?
Carefully pour it into a conical flask.
What is the importance of attaching the delivery tube and gas syringe quickly?
To prevent any gas from escaping.
When should the stopwatch be started in the experiment?
Immediately after adding the marble chips to the flask.
What should be done at regular intervals during the reaction?
Take readings of the volume of gas produced and record them in a table.
How accurate are gas syringes in measuring gas volume?
Gas syringes give volume to the nearest milliliter, making them quite accurate.
What must be kept constant when repeating the experiment with different concentrations of acid?
The mass of marble chips, temperature, and all other variables.
What does a higher volume of gas produced in a set time indicate?
A faster rate of reaction.
What materials are involved in the reaction that produces a yellow precipitate?
Sodium thiosulfate and hydrochloric acid.
What visual cue indicates the reaction between sodium thiosulfate and hydrochloric acid?
The black cross disappearing through the solution.
How can the mass balance be used to measure the amount of gas produced?
As gas forms and escapes, the mass of the reaction mixture decreases.
What does a quicker drop in mass on the balance indicate?
A faster rate of reaction.
What is a drawback of using a mass balance for this experiment?
It releases gas into the room, which is not safe if the gas is toxic.
What is the relationship between concentration of acid and time taken for a reaction?
Higher concentration of acid results in less time for the reaction to occur.
Fill in the blank: A gas syringe measures the _______ of gas produced in a reaction.
volume
True or False: The faster the mark disappears in the sodium thiosulfate and hydrochloric acid reaction, the faster the reaction.
True
What should be done if the gas produced in the reaction is toxic?
Ensure proper ventilation or use a closed system to contain the gas.
What gas is released in the reaction being investigated?
Sulfur dioxide
This reaction requires a well-ventilated area due to the release of sulfur dioxide.
What equipment is mentioned for measuring gas in the experiment?
Gas syringe
The gas syringe is used to measure the volume of gas produced in the reaction.
What safety equipment is recommended for the experiment?
Safety goggles and lab coat
These items are essential for ensuring safety while conducting the experiment.
What is the relationship between concentration of HCl and time taken for the mark to disappear?
Higher concentration leads to faster reaction
As the concentration of HCl increases, the time taken for the mark to disappear decreases.
Fill in the blank: The concentration of HCl in the experiment is measured in _______.
g/dm3
What should be kept constant in the experiment when changing HCl concentration?
Two factors
Factors such as temperature and surface area of the reactants should be controlled.
True or False: The experiment can be conducted without any safety precautions.
False
Safety precautions are necessary due to the nature of the chemicals involved.
How does the concentration of HCl affect the speed of the reaction?
The higher the concentration, the faster the reaction
This is evidenced by the decrease in time taken for the mark to disappear with increasing concentration.
What was the time taken for the mark to disappear at a concentration of 36 g/dm3?
184 seconds
List the concentrations of HCl used in the experiment.
- 18 g/dm3
- 36 g/dm3
- 54 g/dm3
- 72 g/dm3
What is the effect of using different concentrations of acid in the experiment?
It affects the rate of reaction
The change in concentration alters how quickly the reaction occurs.
What does the type of graph you can draw depend on?
The experiment you did.
What should be placed on the x-axis when drawing a graph of gas volume over time?
Time.
What should be placed on the y-axis when drawing a graph of gas volume over time?
Volume of gas.
How do you indicate the amount of gas produced at each time interval on a graph?
Draw a small cross at each point.
What is the purpose of drawing a line of best fit on a graph?
To represent the overall trend of the data.
Fill in the blank: A tangent helps you compare ______ rates at different points.
reaction.
What is the first step to determine the reaction rate at a specific time on a graph?
Position a ruler at the desired time point.
True or False: The steeper the tangent line on a graph, the faster the reaction rate.
True.
What is the formula for calculating the mean rate of reaction?
Mean Rate = amount of product / time.
In the mean rate formula, what does ‘amount of product’ refer to?
The total mass or volume of product formed.
What does a flat line on a reaction graph indicate?
The reaction has finished.
How can you calculate the mean rate for a reaction from a graph?
Determine the total product formed and divide by the time taken.
What should you do to find the amount of product produced between two specific time points on a graph?
Work out the difference in amount produced.
What is the significance of the term ‘line of best fit’?
It represents the best approximation of the data points in a graph.
What is the formula for calculating the mean rate of a reaction?
Mean rate = amount of reactant used (or product formed) ÷ time
This formula is essential for determining reaction rates.
If a reaction takes 120 seconds and produces 3.0 g of product, what is the mean rate of reaction?
0.025 g/s
Calculation: 3.0 g ÷ 120 s = 0.025 g/s
How can the rate of a gas reaction be measured?
In cm³ rather than in grams
This is important when measuring gaseous products.
What does a flat line on a graph of gas volume indicate?
The reaction has finished
This shows that no more product is being formed.
How do you find the mean rate of reaction between two time points on a graph?
1) Calculate the amount of product formed between the points. 2) Calculate the time difference. 3) Divide the amount of product by the time taken.
This method allows for precise calculation of rates over specific intervals.
If 15 cm³ of gas is produced at 20 s and 19 cm³ at 40 s, what is the mean rate of reaction between these times?
0.20 cm³/s
Calculation: (19 cm³ - 15 cm³) ÷ (40 s - 20 s) = 4.0 cm³ ÷ 20 s = 0.20 cm³/s
True or False: The mean rate of reaction can be calculated using only numerical data.
True
Both numerical data and graphical data can be used to determine the mean rate.
What is the mean rate of a reaction that takes 200 seconds and uses 6.0 g of reactant?
0.030 g/s
Calculation: 6.0 g ÷ 200 s = 0.030 g/s
Fill in the blank: The mean rate of reaction is calculated by dividing the amount of reactant used (or product formed) by _______.
time
This is a fundamental concept in reaction kinetics.
What are reversible reactions?
Reactions that can be reversed.
What symbol indicates a reversible reaction?
-
What happens to the concentrations of reactants in a reversible reaction as they react?
Their concentrations fall.
What is equilibrium in the context of reversible reactions?
The amounts of products and reactants aren’t changing anymore.
What is required for equilibrium to be reached in a reversible reaction?
The reaction must take place in a ‘closed system’.
What does it mean if there are more products than reactants at equilibrium?
The reaction is going in the forwards direction.
What can shift the direction of a reversible reaction?
Changing the conditions (temperature, pressure, or concentration).
What happens to ammonium chloride when heated?
It breaks down to form ammonia and hydrogen chloride.
What type of reaction occurs when heat is taken in?
Endothermic.
What type of reaction occurs when heat is released?
Exothermic.
Fill in the blank: If a reaction is endothermic in one direction, it will be ______ in the other.
exothermic.
What does ‘anhydrous’ mean?
Without water.
What does ‘hydrated’ mean?
With water.
What is a closed system?
A system where none of the reactants or products can escape.
True or False: Equilibrium means there are equal amounts of products and reactants.
False.
What does it indicate if the reaction is at equilibrium?
The rates of the forward and backward reactions are equal.
What is the relationship between endothermic and exothermic reactions in reversible processes?
The amount of energy taken in by the endothermic reaction is the same as the amount given out during the exothermic reaction.
