Analysis of Soda Ash
Hand in:Pre-Lab and Open Acetic Acid spreadsheetToday: Determine the amount of Na2CO3in a sample of Soda AshSoda Ash is made up of Na2CO3and other stuffWe can use the fact that Na2CO3is a base that will react with standardizedHClto calculate % in the original Ash sample:2HCl(aq) + Na2CO3(aq) → 2NaCl (aq) + H2CO3
Analysis of Soda Ash
2HCl+ Na2CO3→ 2NaCl + H2CO3Is actually a two-step process:H+ + CO3-2(aq) →HCO3- (step 1)And thenH+ + HCO3- → H2CO3(step 2)So when you titrate: you will seetwoplateaus andtwoinflection pointsToday, we will determine the 2ndendpoint to determine how muchHClis required to completely titrate all the Na2CO3
HCO3-→H++ CO32-Ka2= 4.7 x 10-11H2CO3→H++ HCO3-Ka1= 4.5 x 10-7
Analysis of Soda Ash
So Today:Set upExcelwith active titration graph – use similar format as last week:Column A –mLofHClColumn B is pHColumn C is derivativeSet up Apparatus Similar to last week including:ring stand, magnetic stirrer, burette holder, burette, pH meter, magnetic stir bar.Acid (HCl) goes in burettesoda ash (about .2 grams) goes in beaker (WRITE VIAL #on datasheet as soon as you begin)add 3-4 drops of methyl orange indicatorCalibrate the pH meter probe with 7 & 4 buffers
Analysis of Soda Ash
Use IndicatorMethyl Orange[Yellow(5),Red(3)] to help with theendpoint – see examples for color change to expectYou will ultimately do 5-6 titrations of the sodaash (enough in the vial)Trial 0AddHClcarefully in order to graph 2 plateaus and find the 2ndendpointDetermine the pH at the endpointTrails 1-4 or 5Simply titrate to THAT pH at the 2ndequivalence pointRecord the volume ofHClto reach that pHMay want to do One or Two titrations to find EXACT pH at 2ndEquivalence PointAt least four titrations to get %Na2CO3“Save as” with different file names for first titration curve(s)
Analysis of Soda Ash
Calculations
2HCl+ Na2CO3→ H2CO3+ 2NaClSIMILAR TO PRE-LAB QUESTION #2
.108 moles
Lab Report Due next LabPeriod
TitlePagePurposeResults- One Titration/Derivative Graph- Data Sheet (with sample calculations)- Present/Staple in order data/calculations were obtained/performed- Significant Figures and Units- Precision and Accuracy(the vials have true values you will be graded against)
Conclusion [ Errors , Improvements ]Individual Checked-Pre-labs
0
Embed
Upload