aneeqa haider ariel tsang carrie fan fabiha nuzhat n.
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Aneeqa Haider, Ariel Tsang, Carrie Fan, Fabiha Nuzhat. GRAVIMETRIC ESTIMATION OF CHLORIDE IONS. Introduction. Chloride ion Cl + e −  Cl − Chloride Results from the combination of Cl 2 with a metal (e.g. NaCl) Reactants: NaCl, AgNO 3. Chloride Ion. Introduction. Gravimetric analysis

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introduction
Introduction
  • Chloride ion
      • Cl + e−  Cl−
  • Chloride
      • Results from the combination of Cl2 with a metal (e.g. NaCl)
  • Reactants: NaCl, AgNO3

Chloride Ion

introduction1
Introduction
  • Gravimetric analysis
      • The set of procedures to determine the quantity of a substance present in the mass of a solid
  • Seven steps
      • Drying and measuring the masses of samples to be analysed
      • Dissolving the sample in distilled water.
      • Precipitating the substance by adding a reagent.
      • Separating the precipitate from the solution by filtration.
      • Washing precipitate free of impurities.
      • Drying precipitate to obtain mass.
      • Determine the amount of the original ion based on the known mass and composition of the precipitate.
introduction2
Introduction
  • Objective: Determine the amount of chloride ions present in a given solution of NaCl using AgNO3 as a reagent.
  • Problem: What is the amount of chloride ions present in 0.2 g of Sodium Chloride (NaCl)?
  • Hypothesis: The number of chloride ions present in 0.2 g of NaCl is approximately 2.06 x 10²¹.
materials
Materials
  • Erlenmeyer Flask (2)
  • Beaker (1)
  • Funnel (1)
  • Ashless Filter Paper (1)
  • Paper Clips (4)
  • Balance
  • 0.2 g of Sodium Chloride -NaCl
  • 3 g of Silver Nitrate - AgNO3(aq)
  • Distilled Water
  • Dropper
  • Test Tubes (2)
  • Bunsen Burner
  • Crucible and lid
  • Crucible tongs
  • Retort Stand
  • Ring Clamp
  • Clay Triangle
  • Safety Goggles
  • Spatula
  • Stirring Rod
  • Graduated Cylinder
procedure
Procedure
  • Formation of the precipitate
  • Filtration of the solution containing the precipitate
  • Measurement of the mass of AgCl by drying the filter paper
  • Measurement of the mass of AgCl by burning the ashless filter paper
formation of the precipitate
Formation of the Precipitate
  • 0.2 g of NaCl was dissolved in Distilled Water in Erlenmeyer Flask
  • 3.4 g of AgNO3(aq) was poured into Erlenmeyer Flask containing NaCl (aq).
  • Solution was put into rest until all the precipitate formed.
filtration of the solution containing the precipitate
Filtration of the Solution containing the Precipitate
  • Filter paper, funnel and Erlenmeyer flask were set up
  • The solution containing the precipitate was poured through the filter paper
  • Washed periodically with Distilled water
measurement of the mass of agcl by drying the filter paper
Measurement of the Mass of AgCl by drying the filter paper
  • Filter paper and precipitate were completely dried
  • Mass of the precipitate:
      • Mass of the filter paper with precipitate -

Mass of the filter paper

measurement of the mass of agcl by burning the ashless filter paper
Measurement of the Mass of AgCl by burning the ashless filter paper
  • Retort stand, ring clamp, clay triangle, and Bunsen burner were set up
  • Filter paper was carefully folded with the precipitate inside, and placed in the crucible
  • Crucible was heated until no more filter paper was left
  • Mass of Precipitate:
      • Mass of crucible, lid & precipitate – Mass of crucible & lid
safety precautions
Safety Precautions
  • General Safety Precautions
  • Safety precautions specific for this experiment:
      • Avoiding contact with Silver Chloride (AgCl)
      • Safety precautions while using the Bunsen burner
observations
Observations
  • Formation of the Precipitate
observations1
Observations
  • Measurement of the mass of AgCl by drying the filter paper
observations2
Observations
  • Measurement of the mass of AgCl by drying the filter paper
calculations known information
Calculations – Known Information
  • Mass used of Sodium Chloride (NaCl):
      • 0.2 g
  • Molar mass of NaCl:
      • 35.45 g/mol
  • Percentage composition by mass of Silver Chloride (AgCl):
      • Silver (Ag) = 75%
      • Chloride (Cl) = 25%
calculations by drying filter paper
Calculations – By Drying Filter Paper
  • Mass of filter paper:
      • 1.04g
  • Mass of filter paper + AgCl:
      • 1.43g
  • AgCl:
      • (1.43g – 1.04g) = 0.39g
  • Mass of chloride ions present:
      • 0.25 x 0.39g = 0.0975g
slide19

Calculations – By Drying Filter Paper

  • Number of moles of chloride ions:

= Mass of Cl

Molar Mass of Cl

= 0.0975g

35.45g

= 0.00275 mol

slide20

Calculations – By Drying Filter Paper

  • Mole = Avogadro's number
      • 6.022 x 1023
  • Number of chloride ions:

= (# of moles) x (Avogadro's number)

= (0.00275) x (6.022 x 1023)

= 1.656 x 1021chloride ions present in 0.2 g of NaCl by drying filter paper

slide21

Calculations – By Burning Ashless Paper

  • Mass of crucible + lid + filter paper:
      • 32.13g
  • Mass of crucible + lid + filter paper + AgCl
      • 32.64g
  • AgCl
      • (32.64g – 32.13g) = 0.51g
  • Mass of chloride ions present:
      • 0.25 x 0.51g = 0.1275g
slide22

Calculations – By Burning Ashless Paper

  • Number of moles of chloride ions:

= Mass of Cl

Molar Mass of Cl

= 0.1275g

35.45g

=0.00360 mol

slide23

Calculations – By Burning Ashless Paper

  • Mole = Avogadro's number:
      • 6.022 x 1023
  • Number of chloride ions:
      • (# of moles) x (Avogadro's number)
      • (0.00360) x (6.022 x 1023)
      • 2.167 x 1021chloride ions present in 0.2 g of NaCl by burning filter paper
how did the law of conservation of mass help predict the amount of cl ions in agcl
How did the Law of Conservation of Mass help predict the amount of Cl ions in AgCl?
  • Law of Conservation of Mass
      • Mass of the reactants = Mass of the products
  • Mass of Cl ions in NaCl (reactant)

= Mass of Cl ion is AgCl (product)

what type of chemical reaction is taking place in this experiment
What type of chemical reaction is taking place in this experiment?
  • Double displacement reaction:

AB + CD → AD + CB 

AgNO3 (aq) + NaCl (aq) → AgCl (s) + NaNO3 (aq)

why does nacl dissolve in water
Why does NaCl dissolve in water?
  • Hydration provides greater stability than lattice energy
  • Hydration shell

Water – dipole moment

why doesn t agcl dissolve in water
Why doesn’t AgCl dissolve in water?
  • More stable as a solid precipitate than separate ions
  • Hydration energy provided is less than lattice energy released when compound forms
what are some properties of agcl
What are some properties of AgCl?
  • White crystalline solid
  • Light sensitive
      • Purple  black
  • Change colour when AgCl  Ag + Cl
  • Dry powder, doesn’t draw moisture from the air
  • Very low solubility
  • MP: 455°C BP: 1550°C
why doesn t an excess amount of agno 3 affect the chemical reaction in the experiment
Why doesn’t an excess amount of AgNO3 affect the chemical reaction in the experiment?
  • AgNO3 is the excess reagent
  • Amount of chloride ions = product
  • In this double displacement reaction all of the NaCl must be used up
  • LR = NaCl : limits amount of AgNO3 used

limits amount of products

  • An excess of AgNO3 will not react since all the NaCl is used up already
why was it necessary to wash off all the impurities from the agcl precipitate
Why was it necessary to wash off all the impurities from the AgCl precipitate?
  • Otherwise, mass of the impurities would be included in the mass of the AgCl precipitate
  • Causes an inaccurate measurement of mass of AgCl
  • Causes inaccurate determination of the number of Cl ions
why were the contents of the crucible slightly gray in colour after heating
Why were the contents of the crucible slightly gray in colour after heating?
  • Contents: AgCl and ashless filter paper
  • Ashless filter paper turned into CO2
  • Remaining content: AgCl
  • AgCl is a white coloured powder at SATP
  • Upon heating, AgCl undergoes decomposition to yield Ag and Cl
percentage yield and error
Percentage Yield and Error
  • Percentage Yield

= Actual Yield x 100 Theoretical Yield

= 80%

  • Percentage Error

= (Theoretical Yield – Actual Yield) x 100 Theoretical Yield

= 20%

conclusion
Conclusion
  • By drying filter paper:
      • Number of chloride ions in 0.2g of NaCl is 1.656 x 1021
  • By burning ashless filter paper:
      • Number of chloride ions in 0.2g of NaCl is 2.167 x 1021
  • Amount of ions present in NaCl = amount of ions present in AgCl
      • Law of Conservation of Mass
sources of error
Sources of Error
  • The reading on the electrical balance was observed to change constantly
      • Due to slight air currents
      • Contents being weighted were extremely light
      • Measured multiple times
  • Small amounts of AgCl were stuck in the flask after attempts to remove it
      • Caused alterations in final mass
      • Inaccurate percentage yield
sources of error1
Sources of Error
  • Ashless filter paper not burned away completely
      • final mass greater than expected
  • Crucible was placed on counter to allow for cooling
      • picked up unwanted particles on the counter
suggestions
Suggestions
  • Use of better quality ashless filter paper that will completely burn away without leaving any unwanted residue
  • Use of clean crucible and lid
  • Minimum transfer of the samples from container to container