1. Aneeqa Haider, Ariel Tsang, Carrie Fan, Fabiha Nuzhat

2.  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

3.  Gravimetric analysis ○ The set of procedures to determine the quantity of a substance present in the mass of a solid  Seven steps 1. Drying and measuring the masses of samples to be analysed 2. Dissolving the sample in distilled water. 3. Precipitating the substance by adding a reagent. 4. Separating the precipitate from the solution by filtration. 5. Washing precipitate free of impurities. 6. Drying precipitate to obtain mass. 7. Determine the amount of the original ion based on the known mass and composition of the precipitate.

4.  Objective: Determine the amount of chloride ions present in a given solution of NaCl using AgNO 3 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.

5.  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 - AgNO 3 (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

6. 1. Formation of the precipitate 2. Filtration of the solution containing the precipitate 3. Measurement of the mass of AgCl by drying the filter paper 4. Measurement of the mass of AgCl by burning the ashless filter paper

7.  0.2 g of NaCl was dissolved in Distilled Water in Erlenmeyer Flask  3.4 g of AgNO 3 (aq) was poured into Erlenmeyer Flask containing NaCl (aq).  Solution was put into rest until all the precipitate formed.

8.  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

10.  Filter paper and precipitate were completely dried  Mass of the precipitate: ○ Mass of the filter paper with precipitate - Mass of the filter paper

11.  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

13.  General Safety Precautions  Safety precautions specific for this experiment: ○ Avoiding contact with Silver Chloride (AgCl) ○ Safety precautions while using the Bunsen burner

14.  Formation of the Precipitate ObjectsMass (g)Calculation Filter paper1.04 g Filter paper with NaCl1.24 g NaCl0.2 g(1.24 g - 1.0 g) Graduated cylinder22.48 g Graduated cylinder with AgNO 3 27.08 g AgNO 3 3.4 g(27.48 g - 22.48 g)

15.  Measurement of the mass of AgCl by drying the filter paper ObjectsMass (g)Calculation Filter paper1.04 g Filter paper with AgCl 1.43 g AgCl0.39 g(1.43 g - 1.04 g)

16.  Measurement of the mass of AgCl by drying the filter paper ObjectsMass (g)Calculation Crucible and lid32.13 g Crucible, lid and contents (AgCl) 32.64 g AgCl0.51 g(32.64 g - 32.13 g)

17.  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%

18.  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

19.  Number of moles of chloride ions: = Mass of Cl Molar Mass of Cl = 0.0975g 35.45g = 0.00275 mol

20.  Mole = Avogadro's number ○ 6.022 x 10 23  Number of chloride ions: = (# of moles) x (Avogadro's number) = (0.00275) x (6.022 x 10 23 ) = 1.656 x 10 21 chloride ions present in 0.2 g of NaCl by drying filter paper

21.  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

22.  Number of moles of chloride ions: = Mass of Cl Molar Mass of Cl = 0.1275g 35.45g =0.00360 mol

23.  Mole = Avogadro's number: ○ 6.022 x 10 23  Number of chloride ions: ○ (# of moles) x (Avogadro's number) ○ (0.00360) x (6.022 x 10 23 ) ○ 2.167 x 10 21 chloride ions present in 0.2 g of NaCl by burning filter paper

24.  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)

25.  Double displacement reaction: AB + CD → AD + CB AgNO 3 (aq) + NaCl (aq) → AgCl (s) + NaNO 3 (aq)

26.  Hydration provides greater stability than lattice energy  Hydration shell Water – dipole moment

27.  More stable as a solid precipitate than separate ions  Hydration energy provided is less than lattice energy released when compound forms

28.  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°CBP: 1550°C

29.  AgNO 3 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 AgNO 3 used limits amount of products  An excess of AgNO 3 will not react since all the NaCl is used up already

30.  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

31.  Contents: AgCl and ashless filter paper  Ashless filter paper turned into CO 2  Remaining content: AgCl  AgCl is a white coloured powder at SATP  Upon heating, AgCl undergoes decomposition to yield Ag and Cl

32.  Percentage Yield = Actual Yield x 100 Theoretical Yield = 80%  Percentage Error = (Theoretical Yield – Actual Yield) x 100 Theoretical Yield = 20%

33.  By drying filter paper: ○ Number of chloride ions in 0.2g of NaCl is 1.656 x 10 21  By burning ashless filter paper: ○ Number of chloride ions in 0.2g of NaCl is 2.167 x 10 21  Amount of ions present in NaCl = amount of ions present in AgCl ○ Law of Conservation of Mass

34.  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

35.  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

36.  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