B. Determination of the molar ofa basic oxide ely to the nearest 0.1 mg about 0.

Question

B. Determination of the molar ofa basic oxide ely to the nearest 0.1 mg about 0.1 g of the basic oxide povided and Weigh out accurately to the nearest 0.1 mg about 0.1 g of the basic oxide provided and transfer the sample carefully to a 125 mL Erlenmeyer flask. Now carefully add with a pipet or buret exactly 25.00 mL of the standard HCl solution. Swirl the flask gently until all of the oxide has reacted. Once all the oxide has reacted, the solution should be clear. However, it may be necessary to warm the mixture to ensure that the sample has reacted completely. Cool to room temperature if necessary, add 4 drops of phenolphthalein indicator, and titrate with the standard NaOH solution until a faint pink color is obtained. Repeat the determination with another accurately sample of the basic oxide. From your results calculate the equivalent weight of a basic oxide as s%20of%203%20Bssic%20Oxide.doc%3B%20Expt%20055.doc https://bbhosted.cuny.edu/bbcswebdav/pid-25465017-dt-cont

Explanation / Answer

Method of determination of molar mass of basic oxide

Mass of sample = 0.104 g

Lets say we are using 0.2 M of standard acid solution and 0.1 M NaOH solution

[pl. note molarity of HCl and NaOH solution has to be checked]

Volume of NaOH added = 41.6 ml (Trial 1)

moles of NaOH added = 0.1 M x 41.6 ml = 4.16 mmol

Volume of HCl added = 25 ml

moles of HCl initially added = 0.2 M x 25 ml = 5.0 mmol

moles of HCl reacted = 5 - 4.16 = 0.84 mmol

Equivalent weight of base oxide = 0.104 g/0.00084 mol = 123.81

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