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# TRIPLE Titration

### TRIPLE AQA Chapter 4 Calculations Titrations only

QuestionAnswer
What solution goes in the burette? A solution of KNOWN concentration
What do you use to measure accurately 25cm3? A pipette
Describe the titration procedure Fill the burette; pipette25cm3 of UNKNOWN into conical flask; add indicator in flask; open tap; slow down near the end-point; record volume in burette; repeat until concordant results
What is the end-point? The volume for which there is a colour change in the flask for which there is exactly the same amount of acid particles (H+ ions) as there is of alkali particles (OH-)
What is the number of moles in a beaker containing 25cm3 of a 0.2mole.dm-3 solution? Moles=Conc x vol; CONVERT 25cm3=0.025dm3; Moles=0.025x0.2=0.005moles
What is the volume of 0.025moles of a 0.1mole.dm-3 solution? Vol=Moles/Conc=0.025/0.1=0.25dm3;CONVERT 0.25dm3=250cm3
What is the concentration of a solution of 0.2moles in 20cm3? Conc=moles/vol; CONVERT 20cm3=0.020dm3; Conc=0.2/0.020=10moles.dm-3
C6H8O7 + 3 NaOH ⟶ C6H5O7Na3 + 3 H2O 25cm3 of NaOH of concentration 0.102 mol / dm 3 was used to titrate Citric acid. 12.1cm3 of Citric Acid was used at end-point. Calculate the concentration of the citric acid in mol / dm 3 Sucue; show path;shywio and CONVERT 25cm3=0.025dm3 and 12.1cm3=0.0121dm3; moles=concxvol=0.025x0.102=0.00255; ratio=3:1 so moles acid=0.00255/3=8.5x10^-4; conc=mol/vol=8.5x10^-4/0.0121=0.0702mol.dm-3
31.0 cm3 of KOH neutralised 25.0 cm3 of HNO3. The concentration of the dilute nitric acid was 2.0 moles per dm3. HNO3 + KOH --> KNO3 + H2O Calculate the concentration of the KOHin moles per dm3 Sucue; show path;shywio and CONVERT 25cm3=0.025dm3 and 31cm3=0.031dm3; moles=concxvol=0.025x2.0=0.05; ratio=1:1 so moles KOH=0.05; conc=mol/vol=0.05/0.031=1.613mol.dm-3
NaOH(aq) + HCl(aq) --> NaCl(aq) + H2O(l) 27.20 cm3 of 0.100 moles per dm3 sodium hydroxide neutralised 5.00 cm3 of hydrochloric acid. Calculate the concentration of the hydrochloric acid in moles per dm3. Sucue; show path;shywio and CONVERT 5cm3=0.005dm3 and 27.20cm3=0.0272dm3; moles=concxvol=0.0272x0.100=0.00272; ratio=1:1 so moles acid=0.00272; conc=mol/vol=0.00272/0.005=0.544mol.dm-3
Describe how a student could find out the volume of sodium hydroxide solution that reacts with a known volume of acid. Include any measurements the student should make. volume of acid measured using the pipette; acid in flask;sodium hydroxide or acid in burette; indicator in flask; white tile under the flask; slow addition; swirling/mixing; stop when colour of indicator changes; measure volume in burette
What indicator should you use for a titration of unknown Ethanoic Acid by Sodium Hydroxide? Phenolphthalein=weak acid vs strong base; Methyl Orange=strong acid vs weak base; so here as Sodium Hydroxide is a strong base and Ethanoic acid is a weak acid, you should use Methyl Orange
What are concordant results in a titration? Results that are within 0.10cm3 of each other (ie a difference between the highest and lowest value of 0.10cm3 maximum)
How do you work out the average titre in a titration? You ignore the titre (volume) from the rough titration. You only use concordant results (within 0.10cm3)
How many decimal places should you use to record the volumes from a burette? TWO decimal places: the second decimal place should be either a zero (if the bottom of the meniscus is exactly on the line) or a five (if the bottom of the meniscus is inbetween two lines)
What should look at when reading volumes using a burette or a pipette: the top of the meniscus (the bubble)? The middle? Or the bottom? When reading the volume, you should look at the BOTTOM of the meniscus
A student used 20 cm3 of sodium hydroxide solution with a concentration of 0.18 mol / dm3. Relative formula mass (Mr) of NaOH = 40 Calculate the mass of sodium hydroxide in 20 cm3 of this solution Moles=conc x vol; CONVERT 20cm3=0.020dm3; moles=0.020x0.18=0.0036; mass=moles x RFM=0.036x40=0.144g
What indicator should you use for a titration of unknown Sodium carbonate by Hydrochloric acid? Phenolphthalein=weak acid vs strong base; Methyl Orange=strong acid vs weak base; so here as Sodium Carbonate is a weak base and Hydrochloric acid is a strong acid Methyl Orange
What indicator should you use for a titration of unknown Sodium Hydroxide by Hydrochloric acid? Either! Sodium Hydroxide is a strong base and Hydrochloric acid is a strong acid
What is the difference between a burette and a pipette? A pipette measures a known volume of solution whereas a burette measures a varied volume
Created by: ursulinechem2