Writing Chemical Formula Worksheet With Answer Key - Spes Unica Page 24
ADVERTISEMENT
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28Making up the solution
1. Take a watch glass and place it on the balance. Tare the balance (set it
to zero). Carefully weigh out the required mass of substance.
2. Transfer this amount to a beaker. Add water from a wash bottle to
dissolve it. Use some of the water to rinse all the substance off the
watch glass. Do this at least twice.
3. Stir with a glass rod until all the solid is dissolved, then transfer the
solution to the volumetric flask. Use more water from the wash bottle to
rinse out the beaker and the glass rod. Do this at least twice.
4. Add water to just below the line on the volumetric flask. Add the final
drops with a teat pipette to ensure that the bottom of the meniscus is on
the line.
5. Put the stopper on the flask and turn the flask over a couple of
times to mix the solution.
Example: Making up a 0.1 mol/l solution of sodium chloride, NaCl, using a
250ml volumetric flask
1. Number of moles
= concentration x volume in litres
= 0.1 x (250 ÷ 1000)
= 0.1 x 0.25
= 0.025 moles
2. Formula mass of NaCl = 23+35.5
= 58.5g
3. mass = number of moles x formula mass
= 0.025 x 58.5
= 1.4625g
24
ADVERTISEMENT
0 votes
Related Articles
Related forms
Related Categories
Parent category: Education