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AQA A1 Acid and Gas

AQA Acids and Gas collection

QuestionAnswer
In a gas collection procedure, a student uses a 50cm3 measuring cylinder to collect gas with a maximum error of +/-0.5cm3. She collects 18.5cm3. What is the percentage error? %error = maximum error / measurement * 100= 0.5/18.5*100= 2.7% Note: it is the measurement (18.5cm3) that you use; not the maximum volume(25cm3)!
How do you work out the %error, given the measurement and the maximum error? %error= maximum error / measurement * 100
When you collect Carbon Dioxide bubbling through water into a measuring cylinder, the volume is less than expected. Why? Some of the Carbon Dioxide dissolves in water
When you add acid through a tap funnel, the volume expected is more than expected. Why? The acid takes space in the volumetric flask
When you collect a gas over water, what must you not forget? To fill the measuring cylinder thatt will collect the gas!
What is the formula of Nitric Acid? HNO3
What is the formula of Ethanoic Acid? CH3COOH
What is the formula of Sulfuric Acid? H2SO4
What is the formula of Sodium Hydroxide? Na(OH) Do you remember the charge on the Hydroxide ion?
What is the formula of Magnesium Carbonate? Mg(CO3) Do you remember the charge on the Carbonate ion?
What is the formula of Sodium Carbonate? Na2(CO3) Do you remember the charge on the Carbonate ion?
What is the formula of Magnesium Hydroxide? Mg(OH)2
What is the "active chemical" in acids? Hydrogen ion, H+
Define an acid. A proton(H+) donor
Define a base A proton (H+) acceptor
What is the formula of Ammonia? NH3
What is the name and formula of the salt made from Nitric Acid and Sodium Hydroxide? Sodium Nitrate. Easy: look at the first word. Na(NO3). Do you remember the charge on the Nitrate ion?
What is the name and formula of the salt made from Sulfuric Acid and Sodium Hydroxide? Sodium Sulfate. Easy: look at the first word. Na2(SO4). Do you remember the charge on the Sulfate ion?
Define an Alkali. Give an example A base that can dissolve in acid. For example all the Hydroxides
What is the formula of Potassium Hydroxide? KOH
What is a weak base like Ammonia? It is a base because it is only partially dissociated in water. NH3 + H2O <=> NH4+ + OH-
What is a strong base like Sodium Hydroxide? It is a base that is fully dissociated in water. Na(OH)(s) + H2O --> Na+(aq) + OH-(aq)
Define amphoteric. Give an example. A chemical that is able to both accept a proton and donate a proton. For example amino acids have a carboxylic acid group (-COOH) and an amino group (-NH2)
What is the name and formula of the salt made from Sulfuric Acid and Sodium Carbonate? Sodium Sulfate. Easy: look at the first word. Na2(SO4). Do you remember the charge on the Sulfate ion?
What is the equation for the reaction between Sulfuric Acid and Sodium Carbonate? H2(SO4) + Na2(CO3) --> Na2(SO4) + H2O + CO2
What is the equation for the reaction between Sulfuric Acid and Sodium Hydroxide? H2(SO4) + 2 Na(OH) --> Na2(SO4) + 2 H2O
What is the equation for the reaction between Nitric Acid and Calcium Hydroxide? 2 H(NO3) + Ca(OH)2 --> Ca(NO3)2 + 2 H2O
What is the equation for the reaction between Phosphoric Acid and Sodium Carbonate? 2 H3(PO4) + 3 Na2(CO3) --> 2 Na3(PO4) + 3 H2O + 3 CO2
What is the equation for the reaction between Phosphoric Acid and Ammonia? H3(PO4) + 3 NH3 --> 2 (NH4)3(PO4)
What is the equation for the reaction between HydroChloric Acid and Ammonia? HCl + NH3 --> (NH4)Cl
What is the percentage by mass of Nitrogen in (NH4)3(PO4)? 28.2%
What is the percentage by mass of Nitrogen in (NH4)2(SO4)? 21.2%
How do you work out the %by mass of an Element in a Compound? 1)Count the number of atom of that Element in the compound;2)Multiply that number by the RAM;3) divide the mass of all the atoms of that element by the RMM x 100
What is an indicator? A chemical that has a different colour in acidic solutions than in alkaline solutions
What is the end-point of a titration? When the indicator changes colour
What chemical is placed in the burette? A chemical of unknown concentration
What chemical is placed in the conical flask? A chemical of known concentration
What is the outline of the procedure for a titration? 1)Place unknown in a burette;2)Pipette 25cm3 of a known solution in a conical flask;3)add indicator in flask;4)place flask over white tile;5)open tap from burette;6)go dropwise near end point;7)record volume on burette;8)repeat until concordant results
How do you work out unknown concentration of acid, when 18cm3 of Unknown is needed to neutralise given 25cm3 of known concentration of alkali? 1)Work out moles Alkali=conc x vol flask (25/1000;2)Work out moles Acid using stochio.ratio;3)Work out concentration Acid=moles/volume burette(18/1000)
What is the concentration of HydroChloric Acid when 22.75cm3 of acid neutralises 25cm3 of 0.125mol.dm-3 NaOH. Equation: HCl + Na(OH) --> NaCl + H2O 0.137 mol.dm-3
What is the %uncertainty on a 250cm3 volumetric flask that measures +/- 0.8cm3 0.8/250*100=0.32%
What is the %uncertainty on a 50cm3 burette that measured a titre of 21.40 +/- 0.05cm3 [(0.05)*2]/21.40=0.467%; the%error is taken on the TITRE, not on the total capacity of the burette; the titre is worked by DIFFERENCE so the error is doubled
What is the %uncertainty on a 2decimal places balance that measured a mass of 1.32g by difference the uncertainty is half of the smallest division: 0.01/2=+/-0.005g but there were two readings so double the error; the %uncertainty is 0.005x2/1.32*100=0.75%
The %uncertainty on a burette is more than 5%. How could you reduce that percentage? Either reduce the numerator (ie take a more accurate burette; which is not very feasible) or increase the denominator (ie try to get a bigger titre by diluting the solution in the burette)
Created by: UrsulineChem