C6- The Rate And Extent Of Chemical Changes

Question 1

Rate of chemical reaction

Answer 1

How fast the reactants are changed into products

Question 2

Graphs for rate of reaction

Answer 2

Steeper the line the faster the rate of reaction, over the time the line becomes become less steep as reactants are used up

Question 3

Collision theory

Answer 3

The more collisions the faster rhe reaction. The energy transferred during a collision. Particled have to collide with enough energy for the collision to be successful

Question 4

Factors affecting rate of reaction

Answer 4

Temperature, surface area, conentration of a solution, presence of a catalyst

Question 5

Rate of equation equation

Answer 5

Amount of reactant used or of product formed/time

Question 6

Three ways to measure rate of reaction

Answer 6

Precipitation and colour change, change in mass, the volume of gas given off

Question 7

Precipitation and colour change rp

Answer 7

1. Record visual chnage in a reaction if initial solution is transparent and the product is a precipitate which clouds the solution
2. Observe a mark through the solution and measure how long it takes for it to dissappear - the faster the mark dissapears, the quicker the reaction
3. If reactants are coloured and the products are colourless time how long it takes for solution to lose or gain its colour
4. Cant plot graph and results are subjective

Question 8

Change in mass rp

Answer 8

1. Measuring speed of a reaction that produces a gas can be carried out using a mass balance
2. As gas is released disappearing mass is measured
3. Quicker reading drop, faster the reaction
4. Take measurement at regular intervals to plot graph

Question 9

The volume of gas given off rp

Answer 9

1. Use gas syringe to measure the volume of gas given off
2. The more gas given off during time interval the faster the reaction
3. Can make graph when measure at regular time intervals, if reaction too vigoroud the plunger can be blown out

Question 10

Two rates experiment- magnesium and HCl react to produce H2 gas

Answer 10

1. Add set volume of dilute hydrochrloric acid to conical flask and carefully place on balance
2. Add magnesium ribbon to acid and quickly plug the flask with cotton wool
3. Start stopwatch and record the mass on balance tak reading of mass at regular intervals
4. Plot results and repeat with more concentrated acid soltion with other variables staying the same
5. Three graphs show that a higher concentration of acid gives a faster rate of reaction

Question 11

Two rates experiment - sodium thiosulfate and HCl produce a cloudy precipate

Answer 11

1. Two chemicals both clear and they react together to form a yellow precipitate
2. Start by adding a set volume of dilute solution thiosulfate to conical flask
3. Place flask on piece of paper with black cross drawn on it and add dilute HCl to flask start stopwatch
4. Watch black cross dissappear through the cloudy sulfur and time it takes
5. Results show effect of increasing concentration of HCl on rate of reaction, higher concentration quicker the reactiom

Question 12

Reversible reactions

Answer 12

Products react to form their reactants

Question 13

Reversible reactions can be exothermic and endothermic

Answer 13

If reaction is endothermic in one direction, it will be exothermic in the other

Question 14

Le chateliers principle

Answer 14

Idea that if you change the conditions of a reversible reaction at equlibrium the system will try to counteract that change

Question 15

Things that effect position of equlibrium

Answer 15

Temperature, pressure, the concentration of the reactants and products

Question 16

Why temperature effects equlibrium

Answer 16

If you decrease temperature the equlibrium will move in an exothermic direction to produce more heat making more products for exothermic reaction and fewer products for endothermic

Question 17

Why pressure effects equlibrium

Answer 17

If you increase pressure equlibrium trys to reduce it moves in direction where there are fewer molecules of gas, if you decrease the pressure the equlibrium tries to increase it moves in direction where there are more gas molecules

Question 18

How concentration affects equilibrium

Answer 18

Increase concentration of reactants, the system tries to make more products, if you decrease concentration of products the system tries increasing it by reducing amount of reactants