# C5 OCR Gateway B

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• Created by: gmclaren
• Created on: 11-11-15 19:48
What is a mole?
The unit for amount of substance
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How much is one mole?
6 time 10 to the power of 23
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What is the definition of molar mass?
To calculate the relative formula mass and add grams
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What is conservation of mass?
Conservation of mass is the idea that mass is not lost during a reaction, so the amount of reactants at the beginning will be the same as the amount of products at the end
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What is thermal composition?
Reactions were water or gas are lost during heat
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What is an example of a reaction where gas is gained?
Heating magnesium in air to make magnesium oxide
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What is the equation for amount of moles?
mass in g = number of moles x molar mass
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What is the equation for percentage mass?
Percentage mass = mass of element/ mass of compound x 100 OR relative atomic mass of element/relative atomic mass of compound x 100
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What is the definition for empirical formula?
Simples whole number ratio of each type of atom in a compound. For example C2H6 = CH3
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How do you work out the ratio of compound from an experiment?
You work out the masses of the two compounds and then you work out their relative atomic mass. Then you work out the number of moles and then whichever compound has the smallest moles you divide the other compound by that (see book for example)
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How much should you times cm3 to get to dm3?
1000
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What is the equation for concentration?
Concentration (mol/dm3) = number of moles/volume (dm3)
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What is the difference between a solvent and a solute?
A solvent is the liquid that does the dissolving and the solute is the substance that is dissolved
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How do you measure the concentration of a solution?
Concentration is how many solute particles there are in the soloution
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What is dilution?
Where the solution has more solvent added to it
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On GDA's what do some packaging companies do?
They measure the sodium rather than salt, this is therefore misleading
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What is the equation for volume of water to add? (dilution)
Volume of water to add = (starting concentration/target consentartion -1) x starting volume
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What is the equation for concentration?
Concentration = amount/volume
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What pH is an acid?
0-6
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What pH is an alkali?
8-14
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What is the difference between a single indicator and a mixed indicator?
A single indicator is one that just shows whether it is an acid or an alakli, but a mixed indicator is one that shows what pH the solution is.
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Give some examples of single and mixed indicators?
Phenolphthalein and litmus paper - single Universal indicator - mixed
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What is step one in calculating titrations?
Turn all volumes into dm3
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What is step two in calculating titrations?
Calculate the number of moles of the solutions used
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What is the equation for number of moles? (concentration)
Number of moles = concentration x volume
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What is step three in calculating titrations?
Calculate the unknown concentration (remember that the acids and alkali will be in the ratio 1:1)
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What is the limiting reactant?
The reactant that is sued up at the end
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What is the excess reactant?
The reactant that is left over after the experiment
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If we make 40 kg of sodium sulfate, how much limiting reactant is used? Why is this?
40 kg because the limiting reactant is directly proportional to the amount of product produced and because the more particles there are the more collisions there are meaning more product is made
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What is the definition of molar gas volume?
One mole of any gas has a volume of 24dm3 at rtp (room temperature and pressure)
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What is the equation for molar gas volume?
molar gas volume (at rtp) = number of moles x 24
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What is a reversible reaction?
A reaction that can go both ways
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Does the concentration change at Equilibrium?
No, the concentration, pressure and temperature stays the same
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What happens at Equilibrium?
The reactions (reversible) are still going on, however they are going at the same rate. Meaning there is no change in reaction.
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What is a good analogy of Equilibrium?
Walking down an up escalator
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What happens if the concentration of Equilibrium lies to the left?
If the equilibrium lies to the left then the concentration of reactants is greater than products
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What happens if the concentration of Equilibrium lies to the right?
If the equilbirum lies tot he right then the concentration of products is greater than the reactants
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What happens if some of the products from an equilibrium are removed?
More of the reactants are formed to make products - so that the reaction is equal again
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What happens if some of the reactants from an equilibrium are removed from the reaction?
More of the products are formed to make reactants - so that the reaction is equal again
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What is an open system?
A reaction where one or more products can escape
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What is a closed system?
A reaction where no products can escape
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What happens in a closed system where the reversible reactions reach zero?
The forward reaction is very fast and the reversible reaction is zero then as the forward reaction begins to decrease the reverse reaction speeds up, this carries on until the forward reaction and the reverse reaction reach the same rate
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What happens if temperature is increased?
The equilibrium moves to the side that has the least moles
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What happens if the pressure is increased?
The equilibrium moves to the side that is an endothermic reaction
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What materials are needed to make sulfuric acid?
Water, air and sulfur
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What is the first step of the contact process? And what is the word equation to go with this?
The sulfur is burned in the air to make sulfur dioxide - sulfur (l) + oxygen (g) -> sulfur dioxide (g)
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What is the second step of the contact process? And what is the word equation?
Sulfur dioxide reacts with more oxygen to form sulfur trioxide - sulfur dioxide (g) + oxygen (g) ->
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What conditions are needed for step two of the contact process?
A catalyst of vandium oxide, temperature of 450 degrees and atmospheric pressure
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What is the final step of the contact process? And what is the word equation?
Sulfur trioxdie reacts with water to form sulfuric acid - sulfur trioxide (g) + water (l) -> sulfuric acid (aq)
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Why do we need the conditions for step two of the contact process?
The catalyst increase the rate reaction, but it doesn't change the equilibrium
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Do strong acids fully ionise or not?
They fully ionise
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Do weak acids fully ionise or not?
They do not fully ionise, they create an equilibrium mixture
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What pH do strong acids have in comparison to weak ones?
Strong acids have a low pH, whereas weak acids have a low pH
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The higher the Hydrogen ions the....
lower the pH - meaning the stronger the acid is
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What makes a concentrated acid?
A concentrated acid is how many moles there are in dm3 of acid
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A strong acid can... (ionisation)
fully ionise
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A strong acid...(rate of reaction) why?
has a faster rate of reaction than a weak acid because their are more hydrogen ions colliding in a strong acid
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What happens if the same volume and same concentration is used?
If the same volume and same concentration is used then the same volume of gas is produced
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What is electroylosis?
The breaking down of a compound by putting an electrical current through it
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Which part of the electrolysis are hydrogen ions attracted to and why?
The negative side because they are positive, they gain electrons making then neutral and a hydrogen gas
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Why does ethanoic acid have a lower conductivity than hydrochloric acid?
Because in ethanoic acid there are less hydrogen ions available to move around, therefore less ions can carry the charge
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When can ions move?
When they have been heated to a liquid
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How fast are precipitate reactions?
They are extremely quick
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What is the definition of precipitate?
An insoluble product formed in a precipitation reaction
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How do you create a precipitate?
Choose a combination of solutions that will create a precipitate, mix them together. Then filter the mixture using filter paper and wash the solid, then leave this to dry
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What is a spectator ion?
An ion that doesn't take part in the reaction
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## Other cards in this set

### Card 2

#### Front

How much is one mole?

#### Back

6 time 10 to the power of 23

### Card 3

#### Front

What is the definition of molar mass?

### Card 4

#### Front

What is conservation of mass?

### Card 5

#### Front

What is thermal composition?

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