Penyediaan larutan kimia

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.

Penyediaan larutan kimia

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