how to prepare a standard solution (1 Viewer)

[2006hsc]

how do you prepare a standard solution? (yes i used the search function but didnt find anything)

 

[theworldisround]

1. Weigh out a certain amount of Na2CO3 (let's say 4 grams) in watchglass
2. If you're really pedantic, heat it in oven and cool it in a dessicator, and reweigh.
3. Transfer Na2CO3 into beaker, and add some deionised water to dissolve it.
4. Transfer solution into a 250mL volumetric flask
5. Add distilled water to the volumetric flask until the meniscus lies on the graduated mark.
6. Place stopper over volumetric flask and shake like hell.

To calculate the concentration of this Na2CO3 standard solution, first find the number of moles of Na2CO3.

Assuming 4 grams was weighed out. n = 4 / 106 <-- molar mass of sodium carbonate

Therefore no. of moles = 0.03773...

Concentration = 0.03773 / 0.25 = 0.15 M

0.15M standard solution of sodium carbonate was prepared.

 

[2006hsc]

thankyou!
im assuming u just used Na2CO3 as an example and any solution could be prepared as a standard solution

 

[theworldisround]

Na2CO3 was the standard we used at school. Appropriate standard solutions should be made with substances that are not affected by moisture in the air, so mass is always constant. Also, substances that have a high molecular mass are also appropriate for making standard solutions.

 

[tristambrown]

we used oxalic acid - it was easy to weight out, didnt absorb moisture for the air and it's cheap..