Barium nitrate solutions

Barium nitrate solutions: Is a 0.1M solution of barium nitrate permissible for years 7-10 in NSW Department of Education Schools? It is not clear in the CSIS chemical search. What percentage is a 1M solution of barium nitrate and is it a saturated solution? Can I make up a 0.5M solution of barium nitrate?

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Publication Date: 21 February 2019
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Barium nitrate solutions

As you are in a NSW Department of Education (DoE) school, you are required to follow the directives of your jurisdiction.  The Chemical Safety in Schools (CSIS) package in the NSW DoE states that the user group for barium nitrate solid and solutions greater than 1% w/v is years 11–12. Years 7–10 are only permitted to use barium nitrate solutions of less than 1% w/v. 1

The CSIS package often refers to the concentration as a percentage and many schools refer to the concentration of solutions using molarity. Therefore, we need to consider what percentage a 0.1M solution is and if its concentration is <1% w/v. We could also consider what molar solution is equivalent to a 1% w/v solution:

In brief:

• a 0.1M solution of barium nitrate is greater than a 1% solution and is not permitted for years 7–10 in NSW DoE schools
• It is not possible to make up 1M and 0.5M solutions of barium nitrate as the amount required will not dissolve.
• A saturated solution of barium chloride at 25°C is approximately 10.1% or 0.38M

Some suggestions:

• Prepare a 0.1M solution and then dilute this to make 0.025M solution (<1%)
• Prepare a 0.9% solution of barium nitrate to provide a solution <1% (equivalent of 0.038M)
• If you are conducting a precipitation activity to identify cations and anions, you could substitute with a 0.1M solution of barium chloride, which is permitted for use by years 7–10 in NSW DoE schools
• Where possible use microscale techniques

Molarity, percentage and saturated solutions

Molarity indicates the number of moles of solute dissolved in a litre of the solution; has the symbol M, and the unit, moles per litre (mol/L).

Percentage concentration indicates the mass (or volume) of solute dissolved (or diluted) in 100g or mL, as appropriate, of the solution. It can be expressed as %w/v, %v/v or %w/w.

A saturated solution is one in which, at the temperature specified, no more solute can be dissolved in the solvent.

Science ASSIST has prepared some Laboratory Notes for the preparation of solutions, which contain more detail on calculating concentrations of solutions. See https://assist.asta.edu.au/resource/4415/laboratory-notes-preparing-chem...

Barium nitrate solutions

Molecular formula: Ba(NO3)2

Molecular weight of barium nitrate is 261.3

Solubility: 10.1g per 100mL at 25C

The following table compares the concentration expressed as molarity and by percentage and the required mass for different volumes.

 Concentration  (Molarity) Concentration (% w/v) Final volume of solution       100mL        250mL        1000mL 0.1M 2.613 2.61g 6.53g 26.13g 0.5M (not soluble) 13.1 (not soluble) NA NA NA 1.0M (not soluble) 26.13 (not soluble) NA NA NA 0.038M 1.0 1g 2.5g 10g Saturated (25°C) Approx. 0.39M Saturated (25°C) Approx. 10.1% 10.1g 25.3g 101g

What percentage solution is a 0.1M solution of barium nitrate?

0.1M solution requires 2.61g in 100mL, which is the equivalent of 2.61% w/v

Therefore a 0.1M solution is greater than a 1% solution and is not permitted for years 7–10 in NSW DoE schools

What molar solution is equivalent to a 1% w/v solution of barium nitrate?

A 1% w/v solution means that 1g is dissolved in 100mL water or 10g is dissolved in 1000mL

Number of moles of a chemical = mass chemical/molecular weight

Number of moles in 10g of barium nitrate =10g/261.3g =0.038 moles

Molarity of 10g of barium nitrate in 1 litre = 0.038M

Therefore a 0.1M solution is greater than a 0.038M solution and is not permitted for years 7–10 in NSW DoE schools.

In summary: the concentration that is permitted for years 7–10 in NSW DoE schools needs to be below a 0.038M solution or less than 1g/100ml (we suggest that you prepare either a 0.025M solution; 0.9% w/v solution 0.9g/100mL or a 0.8% w/v solution 0.8g/100mL)

Saturated solution of barium nitrate

The solubility of barium nitrate is 10.1g/100mL water at 25°C.

Therefore, it is not possible to dissolve more than 10.1 g in 100mL water at 25°C, so it is not possible to make up 1M and 0.5M solutions of barium nitrate as the amount required will not dissolve.

Alternatives

If you are conducting a precipitation activity to identify cations and anions we suggest that you use a 0.1M solution of barium chloride. Barium chloride is more soluble in water than barium nitrate and a 0.1M solution of barium chloride is permitted for use by students in years 7–12 in NSW Department of Education schools.

In addition, we suggest that you consider doing it on a microscale, by using one drop of each solution on an acetate sheet (like an overhead projector sheet) or spotting tile, or a laminated white or black sheet of paper (that will show up the precipitate clearly). This reduces the amount of toxic/heavy metal waste produced and can be simply washed off or cleaned with a tissue or paper towel.

Barium chloride solutions

Molecular formula: BaCl2.2H2O

Molecular weight of barium chloride is 244.26

Solubility: 37g per 100mL at 25C

The following table compares the concentration expressed as molarity and by percentage and the required mass for different volumes.

 Concentration  (Molarity) Concentration (% w/v) Final volume of solution       100mL            250mL           1000mL 0.1M 2.44 2.45g 6.11g 24.43g 0.5M 12.21 12.21g 30.53g 122.13g 1.0M 24.43 24.43g 61.07g 244.26g 0.041M 1 1g 2.5g 10g Saturated (25°C) Approx. 1.5M Saturated (25°C) Approx. 37% 37g 92.5g 370g

Saturated solution of barium chloride

The solubility of barium chloride is 37g/100mL water at 25°C.

Therefore, it is not possible to dissolve more than 37g in 100mL water at 25°C, however it is possible to make up a 1M and 0.5M solution of barium chloride as the amount required will dissolve.