# C5 OCRgateway

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• Created by: Dkang
• Created on: 22-02-16 19:46
What does one mole of a substance weigh?
One mole of any atom of any substance will have a mass in grams equal to the relative formula mass
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What does one mole of Carbon weigh?
12g
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How can I work out the number of moles?
Number of moles = Mass (g) / Mr
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What is the relative atomic mass of an element?
The relative atomic mass of an element is the average mass of an atom of the element compared to the mass of 1/12 of an atom of CARBON-12
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How can I use moles to find out the mass?
1)Write balanced equation 2)Calculate number of moles of one you know most about 3)Use a ratio to find number of moles of other element 4)Use the formula for mass
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What can I use to find out the percentage composition by mass?
Percentage composition by mass = mass of element / mass of compound x 100
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How do I work out the empirical formula?
1)Divide the given mass of each element by its relative atomic mass 2)Divide both answers by the smallest answer 3)Put numbers into their appropriate place
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What is concentration?
Concentration is how much solute is in a given volume measured in dm^3
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What is the formula to work out the concentration
Concentration = moles/volume
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What are titrations?
They allow you yo find out how much acid is needed to neutralise an alkali (vice versa)
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Why are single indicators used as opposed to universal indicators?
As you want to see a sudden colour change so a single indicator is best whereas a universal indicator has a wide range of colours therefore only gradually changes colour
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What would the graph of an acid being added to an alkali look like?
There is a gradual decrease in pH as the acid is added, the end point comes suddenly shown as an almost vertical line, the graph begins to level off
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What is one way to collect gas?
A gas syringe which can collect most gases and are quite accurate (cm3), however if the reaction is too vigorous the plunger can blow out of syringe
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What is another way to collect gas?
An upside down measuring cylinder, it is not good at collecting ammonia or hydrogen chloride as they dissolve in water
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How can you measure the mass of gas?
Using a mass balance, as the gas is released the mass disappearing can be measured on the balance. However it releases gas straight into the room.
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What volume does one mole of gas occupy?
One mole of any gas always occupies 24dm^3 at room temperature (25oc) and pressure (1 atmosphere)
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How would you work out the volume using room temperature?
Volume = moles x 24
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What is a limiting reactant?
The reactant that is all used up in the reaction
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How much product would be formed?
The amount of product formed is directly proportional to the amount of limiting reactant
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What does a steeper line on a graph represent?
It represents a faster rate of reaction
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What will all reversible reactions reach?
Equilibrium
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What must the reversible reaction take place in?
A closed system where no reactants or products can escape
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If there is a higher concentration of products than reactants which side will the equilibrium lie to?
The right
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How does a decrease in temperature affect the position of equilibrium?
The equilibrium will move in the exothermic direction (forward) to increase it
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How does an increase in pressure affect the position of equilibrium?
The equilibrium will move in the direction where there are fewer moles to reduce it
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How does an increase in the concentration of the products affect the position of equilibrium?
The equilibrium moves to the left to decrease it
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What is the contact process used for?
The contact process makes sulfuric acid
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What is the first stage of the contact process?
Making sulfur dioxide by burning oxygen in air (sulfur + oxygen --> sulfur dioxide)
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What is the second stage of the contact process?
Sulfur trioxide is made by oxidising sulfur dioxide (sulfur dioxide + oxyen --> sulfur trioxide)
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What is the third stage of the contact process?
Sulfuric acid is made using sulfur trioxide (sulfur trioxide + water --> sulfuric acid)
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Which stage of the contact process is reversible?
The second stage where sulfur trioxide is made
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In stage 2 what would the optimum temperature used be?
450 degrees as the reaction is exothermic so the temperature should be reduced but not so much it slows the rate of reaction down
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In stage 2 what would the optimum pressure used be?
1 atmosphere as pressure should be increased to shift equilibrium to the right but it is expensive and not neccessary
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In stage 2 what catalyst would be used?
V2O5 as it increases the rate of reaction but doesn't change the position of equilibrium
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What is a strong acid?
An acid that completely ionises in water so every hydrogen atom releases a hydrogen ion
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What is a weak acid?
An acid that doesn't fully ionise in water so only some hydrogen atoms release hydrogen ions
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What is different about the ionisation of a weak acid?
It is a reversible reaction so sets up an equilibrium mixture which lies to the left
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What does acid strength mean?
The proportion of the acid molecules that ionise water
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What does the acid concentration mean?
How many moles of acid there are in 1dm^3 of water
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Why are strong acids better conductors than weak acids?
As strong acids have a higher concentration of ions so more charge can be carried
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Why do strong acids react faster than weak acids?
As strong acids has more ions for the reactants to react with increasing the collision frequency
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Why would the same volume of gas be produced by a strong and weak acid?
If the same concentration and volume of acids is used the volume of gas produced will be the same as both acids contain the same number of moles
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What does a precipitation reaction consist of?
Two solutions reacting to make an insoluble substance called a precipitate
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Why are precipitation reactions so fast?
There are lots of ions to react that can move causing a high collision frequency
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How can you tell from an ionic equation that it's a precipitation reaction?
If you start with two solutions (aq) and end up with a solid (s)
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What is barium chloride used to test for?
Used to test for sulfate ions, if a white precipitate forms
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What is nitric acid/lead nitrate used to test for?
Used to test for chloride(white precipitate), bromide(cream) or iodide(yellow)
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## Other cards in this set

### Card 2

#### Front

What does one mole of Carbon weigh?

12g

### Card 3

#### Front

How can I work out the number of moles?

### Card 4

#### Front

What is the relative atomic mass of an element?

### Card 5

#### Front

How can I use moles to find out the mass?

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