Chemistry - Everything C5 for the OCR Gateway exam!

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How does 1 Mole of an atom or molecule affect the mass in grams of a substance?
One mole will have an equal mass in grams to the relative formula mass of the substances used
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What is the formula for finding the number of moles in a given mass?
Mass in G (Element or compound) / Relative formula mass (of element or compound)
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What is the definition of relative atomic mass in terms of Carbon-12?
The Relative atomic mass of an element is the average mass of an atom of the element compared to the mass of 1/12th of an atom of Carbon-12
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What are the four steps to calculating the mass of a reaction, using moles?
1) Write balanced equation 2) Calculate no of moles of element 3)Look at ratio of moles in the equation 4) Calulate mass of ratio of moles in product
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How do you work out the percentage composition by mass of compounds?
(Relative atomic mass X no. of atoms (of element) / relative formula mass) X 100
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What are the five steps in working out Emperical Formulas?
1) List elements in compoud 2) Write experimantal mass or % 3) Divide mass by relative atomic mass 4) Multiply by well chosen numbers 5) Get Ratio in simplest form
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What is the formula to work out concentration (using moles)?
Concentration (mol dm^3) = No. of Moles / Volume (dm^3)
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What is the formula for converting moles per dm^3 to Grams per dm^3?
Number of moles = mass (g) / Relative Formula Mass
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What are the three steps in diluting a concentrated solution?
1) Work out the Ratio of the two concentrations ( small/big) 2) Multiply Ratio by volume of solution you want to end up with 3) Work out vol of water needed: total volume - volume to dilute
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What are the two steps in estimating salt content from sodium?
1) Find ratio of sodium chloride (salt) relative formula mass / relative atomic mass of sodium 2) Multiply by amount of Sodium in food
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What do Titrations allow?
Allow you to find out exactly how much acid is needed to nuetralise a quantity of alkali (Vice Versa)
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What six things do you need for a Titration experiment? (equipment)
1) Conical Flask 2) Burette 3) Pipette with pipette filler 4) Acid 5) Alkali 6) Indicator
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What sort of Indicator should you use in a titration experiment?
Litmus Paper (blue in alkalis, red in acids)
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How do you ensure accuracy in a titration experiment?
-Repeats -Use a single indicator (not universal)
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What do pH curves show?
pH against Volume of acid or alkali added
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What formula do you use to work out the concentration of an acid in a titration experiment?
Concentration = No. of Mole / Volume
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What are the three steps in working out the concentration of an acid in a titration experiment?
1) Work out moles of known sustance 2) Write balanced symbol equation and work out moles of Unknown substance 3) Work out concentration of unknown substance
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What is a disadvantage of using an Upturned measuring cylined or burrette to calculate Gas volumes?
Is filled with water so some substances (such as Hydrogen chloride and ammonia) dissolve in water
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Which is the most accurate way to measure volume of gas and why?
Measuring mass of gass produced, because the mass balance is very accurate
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How much (in dm^3) volume does one mole of gas occupie at room temperature and pressure?
24dm^3
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What is the formula for working out volume of gas in terms of moles?
Volume = No. of moles X Volume of 1 mole (24)
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What is a reversible reaction?
Where the products of a reaction can react to produce the original reactants
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What is Equilibrium?
When the rate of reation of the forward reaction is equall to the rate of reaction of the backwards reaction
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What do the conditions have to be like for Equillbrium to take place?
Reaction has to take placed in 'Closed System' so no reactants of products are lost
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What does it mean if the equilibrium is lying to the right?
Concentration of products is higher than the concentration of reactants
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What does it mean if the equilibrium is lying to the right?
Concenration of reactants is higher than concentration of products
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What are the three things that could change the position of the equilibrium?
- Temperature - Concentration - Pressure (only if gas involved)
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Does a catalyst change the equilibrium position? Why/why not?
No - Catalyst speeds up forward and backward reaction by the same amount, so the same amount of product is made, as would have been without the equilibrium
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What does an equilibrium do if conditions are changed?
It counteracts the change, eg, if temp decreased, equilibrium temp will increase
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How does temperature affect an equilibrium and why?
Equilibrium does opposite of temp change due to exothermic and endothermic reactions: Reaction = Exothermic on way, endothermic other. Will move to exothermic direction to produce heat and move to endothermic direction to deacrease heat
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How does pressure affect an equilibrium and why?
High pressure - equilibrium will reduce it by moving in direction of less moles of gas (and vice versa)
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How does concentration affect an equilibrium and why?
Increasing concentration of product of reactants cause equilibrium to decrease concentration by shifting to right (to create more produce) and vice versa
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What does the contact process make?
Sulfuric Acid
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What are the three stages of the contact process?
1) Make Sulfur dioxide by burning sulfur in air 2) Sulfur Dioxide is oxidised by a catalyst to create sulfur trioxide 3) Sulfur trioxide added to water creates sulfuric acid
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What are the three equations for each stage of the contact process?
1) Sulfur + Oxygen = Sulfur Dioxide 2) Sulfur Dioxide + Oxygen == Sulfur trioxide 3) Sulfure trioxide + water = sulfuric acid
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What type of reaction is oxidising sulfur dioxide to form sulfur trioxide
Exothermic
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What do acids produce, due to them being ionising?
Hydrogen Ions
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What do strong acids do in water?
Ionise completely in water so lots of H+ Ions are produced
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What happens to weak acids in water?
Do not fully ionise, so only small amounts of H+ ions are produced
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What type of reaction is the ionisation of a weak acid?
A reversible reaction = equilibrium reaction
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Where does ionisation of a weak acid lie and why?
Lies to the left of eqilibrium because only a few H+ ions are produced
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What does the strength of an acid tell you?
What proportion of the acid molecules ionise in water
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What does the concentration of an acid tell you?
How many moles of acid there are in a litre of water (more moles, more concentrated)
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Are strong or weak acids better for electrical conduction and why?
Strong acids - because they have a higher concentration of H+ ions which carry the charge though the liquid
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Why does the electrolysis of hydrochloric acid or ethanoic acid produce Hydrogen?
Because they both produce H+ ions
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What is produced when hydrochloric or ethanoic acid reacts with magnesium?
Hydrogen
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What is made when hydrochloric or ethanoic acid reacts with calcium carbonate?
Carbon dioxide
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Will a strong or weak acid have a higher rate of reaction?
Strong acid - because all of the acid molecules are ionised so there are lots of H+ ions, waiting to react. There will be a higher frequency of succesful collisions
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What does Aqeus (aq) mean?
Is dissolved in water
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What is a precipitate reaction?
Where two solutions react together to make an insoluble substance
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What is the precipitate in a precipitate reaction and what does it do to the solution?
Is the insoluble substance - turns solution cloudy
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Are precipitate reactions quick or slow and why?
Quick - High frequency of succesful collisions between ions
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What are spectator ions?
Ions that do not change during a reaction
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What colour does the precipitate of barium chloride have to be if sulfate was the original compound?
White
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How do you test for chloride (halides) in a reaction?
Add dilute nitric acid then add lead nitrate
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What can precipitate reactions be used for?
Making insoluble salts
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How do you make an insoluble salt? (2 steps)
1) Place ions in solution to allow movement 2) Mix together to create insoluble salt
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What are the three steps in fininshing the creation of an insoluble salt?
1) Precipitate - add lead nitrate and distilled water together, then same with iodide, mix two solutions. 2) Filter - using funnel and filter paper 3) Rinse and Dry
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What is an example of the reaction to create an insoluble salt?
Lead Nitrate + Potassium iodide = lead iodide + potassium nitrate
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What is needed to make lead iodide?
-Lead ions (lead nitrate) - Iodine ions (Potassium) - Solution
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Other cards in this set

Card 2

Front

What is the formula for finding the number of moles in a given mass?

Back

Mass in G (Element or compound) / Relative formula mass (of element or compound)

Card 3

Front

What is the definition of relative atomic mass in terms of Carbon-12?

Back

Preview of the front of card 3

Card 4

Front

What are the four steps to calculating the mass of a reaction, using moles?

Back

Preview of the front of card 4

Card 5

Front

How do you work out the percentage composition by mass of compounds?

Back

Preview of the front of card 5
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