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5/20/2018 Penyediaan larutan kimia
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Penyediaan larutan kimia
Bagaimana mengira kemolaran daripada
kepekatan reagen komersial.
Contohnya terdapat label pada botol ais sulfurikkormesial :
Specific Gravity = 1.84
Percentage = 96
Kirakan kemolaran of H2SO4 .
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Penyelesaian:
Ketumpatan H2SO4 = 1.84g/ 1ml
Jisim molekul relatif dalam gram = 98g
Berat H2SO4 dalam 1ml= 1.84g/ 1ml x 96/100
= 1.77g
Berat H2SO4 dalam 1l = 1.77g/ 1ml x 1000ml/1l
= 1770g/lKemolaran H2SO4 = 1770 / 98
= 18 M
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Activiti:
Kirakan kemolaran asid hidroklorik, diberi
spesifik gravitinya 1.18 dan peratusan 36
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Solution:
Density of HCl= 1.18g/ 1ml
Relative molecular mass in grams = 36.5g
Weight of HClin 1ml= 1.18g/ 1ml x 36/100
= 0.425g
Weight of HClin 1l = 0.425g/ 1ml x 1000ml/1l
= 425g/lMolarity of HCl = 425 / 36.5
= 11.6M
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Preparation of Stock Solution
Stock solutions are usually prepared from
commercial concentrations by using this
formula:
M1V1= M2V2
M1= Molarity of concentrated solutionV1= Volume of concentrated solution
M2= Molarity of dilute solution
V2 = Volume of dilute solution
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Example
A dilute solution of sulphuric acid is to beprepared from concentrated solution.
How many mlof 18MH2SO4 is required to make
120ml3M H2SO4 ?
Solution:
M1= 18M ; V1=? ; M2 = 3M ; V2= 120ml
V1 = M2V2 = 3 x 120 = 20ml
M1 18
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Activity:
If you have stock solution of 2M hydrochloric
acid, explain how you can prepared 500ml0.1M
hydrochloric acid from the stock solution.
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Solution:
M1= 2.0M ; V1=? ; M2 = 0.1M ; V2= 500ml
V1 = M2V2 = 0.1 x 500 = 25ml
M1 2.0
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Procedures:1. Fill the 500ml volumetric flask with
about 20mlof distilled water.
2. Pipette 25mlof hydrochloric acid into
the volumetric flask.
3. By using the wash bottle, fill the
volumetric flask with distilled water
until the liquid meniscus is even withthe graduated mark.
4. Cocked and shake the volumetric
flask.
Pipette
Volumetric
Flask
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Activity:
Preparing 100 ml of 2.0 M standardsodium hydroxide solution.
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Procedures:1. 8.0 g of solid sodium hydroxide is weighed.
2. Transferred 8.0g of sodium hydroxide into a beaker
containing about 25.0 cm3of distilled water. The mixture
is stirred well to dissolve the solid.
3. The solution from the beaker is then carefully poured into
a 100 cm3volumetric flask through a filter funnel.
4. Fill the volumetric flask with distilled water until theliquid meniscus is even with the graduated mark.
5. Cocked and shake the volumetric flask.
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