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A solution containing 0.400 g of a diprotic acid requires 40.00cm^3 of 0.100 mol dm^3...

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roshan-rox | Valedictorian

Posted May 7, 2013 at 6:44 AM via web

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A solution containing 0.400 g of a diprotic acid requires 40.00cm^3 of 0.100 mol dm^3 NaoH solution for complete neutralization.What is the approximate relative molecular mass of the acid?

(1) 5.00 × 10

(2) 1.00 × 10^2

(3) 2.00 × 10^2

(4) 3.00 × 10^2

(5) 4.00 × 10^2

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jeew-m | College Teacher | (Level 1) Educator Emeritus

Posted May 7, 2013 at 6:59 AM (Answer #1)

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A diprotic acid is a acid that have the capability to provide two `H^+ ` ions to the solution such as `H_2SO_4` . Let us take the acid as `H_2A`.

`2NaOH+H_2A+ rarr Na_2A+2H_2O`

Amount of NaOH used for reaction `= 0.1/1000xx40 = 0.004mol`

 

Since 0.004moles of NaOH reacted the amount of diprotic acid moles reacted will be half of NaOH reacted.

`NaOH:H^+ = 2:1`

 

Amount of diprotic acid reacted `= 0.004/2 = 0.002mol`

 

Relative molecular mass

= (mass)/(mol)

`= 0.4/0.002 `

`= 200 `

`= 2xx10^2`

 

So the answer is (3)

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