Unit 4- Rates Of Reaction

Question 1

When does a chemical reaction take place?

Answer 1

When the particles collide successfully, the reacting particles must collide with enough energy to break the existing bonds

Question 2

What is activation energy

Answer 2

Minimum amont of energy particles must have a successful collision

Question 3

What is the formula for rate

Answer 3

Rate = volume of gas / time

Question 4

Explain the effect of changing the surface area for rates of reaction

Answer 4

• The larger the surface, more particles can collide per second
• you get a larger surface area by breaking a solid down
• by breaking a solid down this does not effect the product you get at the end
• but you do get a faster rate of reaction

Question 5

Explain the effect of changing the concentration in terms of rate of reaction

Answer 5

• If you increase the concentration you increase the rate
• If you double the concentration you double the rate
• rate is directly proportional to concentration
• when you increase the concentration, you increase the number of particles which are reacting with each other so there are more frequent Collions

Question 6

Explain the effect of pressure on rate of reaction

Answer 6

The pressure can alter the rate of reaction, especially with gasses. When the pressure is increased it will increase the rate of the reaction because there will be less room for the particles so there will be more frequent collisions. When you increase the pressure you decrease the volume of the gas so the particles are closer together

Question 7

Explain the effect of temperature on rate of reactions

Answer 7

• Reactions occur quicker when heated
• When the temperature increase the rate of reaction increases
• When the particles heat up the gain more energy and start to vibrate. So there are more frequent collisions because the particles are moving quicker and the Collions have more force so more of them are successful

Question 8

Explain the effect of catalyst on rate of reaction

Answer 8

• A catalyst is a chemical, which increases the rate of a chemical reaction, but is left chemical unchanged at the end
• it does not change what you get or how much, catalyst remain unchanged at the end
• Enzymes only work for certain reaction but that is not necessary true for catalysts
• Catalyst lower the activation energy

Question 9

Why does a catalyst speed up the rate?

Answer 9

• A catalyst works by allowing the reaction to happen using a different path way which means it has a lower activation energy
• More of the molecules will have energy equal to or greater than the activation energy
• More molecules can collide successfully

Question 10

How can you measure the rate of a reaction

Answer 10

• Measure the change in mass over time, a reaction producing gas can be carried out on a scale, the mad decreases as the gas is released.
• measure the volume of gas released
• measure the formation of a precipitate, if the reaction produces a solid it will cloud the solution. The time it take to become too cloudy to see through it can be measured

Question 11

How do you test for oxygen

Answer 11

If it lights a glowing splint