On a microscale acceptance add solutions containing lithium, calcium and silver cations to solutions containing fluoride, chloride, bromide and iodide anions, and almanac which combinations aftermath an insoluble precipitate. From the after-effects they attack to identify patterns of behaviour amid these anions, and try to explain them.
A well-organised accumulation of students, alive in pairs, should be able to complete the applied date in 10 minutes, accustomed the artlessness of the procedure. Altercation of the after-effects to analyze patterns should booty about the aforementioned time, but added altercation to aftermath explanations will depend on the akin of the class.
Anniversary alive accumulation will need:
Bright acetate area (e.g. OHP sheet), or bright artificial spotting bowl (well-plate) (Note 1)
Solutions (about 2 cm3) independent in artificial pipettes (Note 2)
Silver nitrate, 0.1 M
Lithium bromide, 1 M
Calcium nitrate, 0.4 M
Sodium fluoride, 0.5 M (HARMFUL)
Sodium chloride, 0.2 M
Potassium bromide, 0.2 M
Potassium iodide, 0.2 M
Refer to Bloom & Assurance and Technical addendum area beneath for added information.
Bloom & Assurance and Technical notes
Read our accepted bloom & assurance guidance
Wear eye protection.
Argent nitrate solution, AgNO3(aq) – see CLEAPSS Hazcard and CLEAPSS Recipe Book.
Lithium boiler solution, LiBr(aq) – see CLEAPSS Hazcard.
Calcium nitrate solution, Ca(NO3)2(aq) – see CLEAPSS Hazcard.
Sodium fluoride solution, NaF(aq), (HARMFUL) – see CLEAPSS Hazcard.
Sodium chloride solution, NaCl(aq) – see CLEAPSS Hazcard and CLEAPSS Recipe Book.
Potassium boiler solution KBr(aq) – see CLEAPSS Hazcard.
Potassium iodide solution, KI(aq) – see CLEAPSS Hazcard and CLEAPSS Recipe Book.
1 As an another to acetate sheets, cellophane spotting plates (well-plates) can be used, although may be difficult to obtain. Ordinary white spotting plates should still acquiesce precipitates to be observed, although not as easily.
2 Solutions for microscale abstracts such as this can be stored, distributed, and acclimated in distinctively able artificial pipettes. The starting point is a accumulation of fine-tip artificial pipettes, accessible in aggregate from, for example, Sigma-Aldrich (cat. ref. Z13,503-8). The pipettes are acclimatized as apparent in the diagrams below, abounding with about 2 cm3 of one of the solutions, labelled, and stored as sets of 7 altered solutions in old audio-cassette boxes or added acceptable container. Labels should accommodate hazard information.
a Create and alike a worksheet that can be covered by the acetate sheet, based on this table, scaled up to A4.
Argent nitrate solution
Lithium boiler solution
Calcium nitrate solution
b Cover the worksheet with a bright acetate sheet.
c Put 1 bead of anniversary of the halide ion solutions in the adapted box on the acetate sheet.
d Add one bead of argent nitrate band-aid to anniversary box in the aboriginal column.
e Add one bead of lithium boiler band-aid to anniversary box in the additional column.
f Add one bead of calcium nitrate band-aid to anniversary box in the third column.
g Record all observations in a acceptable table.
h Wash the acetate area beneath the tap and dry with a cardboard towel.
This agreement looks at the similarities and differences in some of the backdrop of the simple halide anions. Anniversary of the halogens forms a singly-charged anion.
Collecting students’ after-effects should confirm:
Depending on their level, acceptance should be able of autograph both academic and ionic equations for the precipitation reactions observed.
NaCl(aq) AgNO3(aq) → NaNO3(aq) AgCl(s)
and the associated ionic equation:
Ag (aq) Cl−(aq) → AgCl(s)
The botheration with lithium fluoride, if encountered, may be due to the aftereffect of ion pairing in solution. This is due to the aerial apparent densities of allegation on both cation and anion, so that the abstracted ion activities are bereft to ability the solubility product. The added lithium halides are all actual soluble.
The accepted cessation is that fluorides behave rather abnormally from the otherhalides. This abnormality is accepted in all Groups, area the aboriginal aspect about has some aberrant properties.
Follow up altercation could focus on accessible affidavit for this, depending on the akin of the chic involved. Important factors include:
However there is a lot added to these phenomena than this, and agents will ambition to adjudicator for themselves the admeasurement and abyss of the altercation that is adapted for the acceptance involved.
Bloom & Assurance checked, 2016
This Applied Chemistry ability was developed by the Nuffield Foundation and the Royal Society of Chemistry.
© Nuffield Foundation and the Royal Society of Chemistry
Page aftermost adapted October 2015
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