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# Chemistry Calculations... Watch

Q2. In order to prepare agar plates you need 20cm3 of nutrient agar solution per plate. The nutrient agar solution is made by dissolving nutrient agar powder in sterile water at a 2.3% concentration.

Q2.1. How much agar powder do you need to weigh out to prepare 55plates? (in grams). Take into account that the typical laboratory balance has an accuracy of 0.001 g.

25.3g ?

Q2.2. How much water do you need to use to prepare 55 plates? (in dm3). Assume that the typical accuracy of laboratory cylinders is 1cm3.

2970dm3??
2. First one looks about right.

Remember 1000cm3 is 1dm3, also the total volume will be 55x20cm3.

Remember 1000cm3 is 1dm3, also the total volume will be 55x20cm3.
Right, I managed to get 0.594dm3...
4. you need to take 1cm3 away from the total for every 1g of solute (it will displace this volume of solvent)
you need to take 1cm3 away from the total for every 1g of solute (it will displace this volume of solvent)
Well, if the total volume is 1100cm3, then 1cm3 removed from the total for every 1g of solute is 55cm which makes 1045cm3 which is 1.045dm3?????
6. what mass of agar (which is the solute) are you adding?
what mass of agar (which is the solute) are you adding?
20cm3, so it's 1080cm3 which is 1.08dm3?
8. (Original post by I Have No Imagination)
25.3g
so the volume is.....
so the volume is.....
1074.7cm3
Thanks a lot!
11. except one little bit i just spotted
(Original post by I Have No Imagination)
Assume that the typical accuracy of laboratory cylinders is 1cm3.
otherwise, no probs

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