Okay, Ruddy, let's present the titration calculations in a clear, step-by-step format.
Titration Calculations
Step 1: Calculate the average volume of hydrochloric acid (HCl) used.
The consistent readings are 23.70cm3 and 18.80cm3.
AveragevolumeofHCl=223.70cm3+18.80cm3
AveragevolumeofHCl=242.50cm3
Average volume of HCl = 21.25\text{ cm^3}
Step 2: Calculate the number of moles of hydrochloric acid (HCl) used.
Given concentration of HCl = 0.100mol/dm3.
Volume of HCl = 21.25cm3=0.02125dm3.
MolesofHCl=Concentration×Volume
MolesofHCl=0.100mol/dm3×0.02125dm3
MolesofHCl=0.002125 mol
Step 3: Write the balanced chemical equation for the reaction.
Assuming solution A is sodium carbonate (Na2CO3):
Na2CO3(aq)+2HCl(aq)→2NaCl(aq)+H2O(l)+CO2(g)
Step 4: Calculate the number of moles of solution A (Na2CO3) in 25.0cm3.
From the balanced equation, the mole ratio of Na2CO3 to HCl is 1:2.
MolesofNa2CO3=2MolesofHCl
MolesofNa2CO3=20.002125mol
MolesofNa2CO3=0.0010625 mol
Step 5: Calculate the concentration of solution A (Na2CO3) in mol/dm3.
Volume of solution A = 25.0cm3=0.0250dm3.
ConcentrationofNa2CO3=VolumeMoles
ConcentrationofNa2CO3=0.0250dm30.0010625mol
Concentration of Na_2CO_3 = 0.0425\text{ mol/dm^3}
Step 6: Calculate the molar mass of Na2CO3.
Atomic masses: Na = 22.99, C = 12.01, O = 16.00.
MolarmassofNa2CO3=(2×22.99)+12.01+(3×16.00)
MolarmassofNa2CO3=45.98+12.01+48.00
MolarmassofNa2CO3=105.99 g/mol
Step 7: Calculate the concentration of solution A (Na2CO3) in g/dm3.
Concentration(g/dm3)=Concentration(mol/dm3)×Molarmass
Concentration(g/dm3)=0.0425mol/dm3×105.99g/mol
Concentration (g/dm^3) = 4.50\text{ g/dm^3} (to 3 significant figures)
Step 8: Calculate the percentage purity of sample A.
Original concentration of sample A = 5.00g/dm3.
Percentagepurity=OriginalconcentrationofsampleAConcentrationofpureNa2CO3×100%
Percentagepurity=5.00g/dm34.50g/dm3×100%
Percentagepurity=0.900×100%
Percentagepurity=90.0%
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