Hi I been attempting some problems and I am stuck on theseones. 1. Determine the

Question

Hi I been attempting some problems and I am stuck on theseones.

1. Determine the mass of H2C2O4 x2H2O needed to make 250 mL of 0.080 MH2C2O4.


2. If 32.96 mL of a NaOH solution are required to tirate 25.00mL of0.08121 M H2C2O4 to the end point,what is the molarity of the sodium hydroxide solution?

3. If 24.92 mL of the NaOH solution from the previous question arerequired to titrate 0.1932g of an unknown diprotic (n=2) acid, whatis the molar mass of the acid?

4. In the standardization of NaOH solution, why is it important torinse the wet pipet with small portions of the standard oxalic acidsolution?



Thanks.

Explanation / Answer

1. Determine the mass ofH2C2O4 x 2H2O needed tomake 250 mL of 0.080 M H2C2O4.
Molar mass of H2C2O4 x2H2O is , M' = 2 * 1 + 2 * 12 + 4 * 16 + 2 (2*1 + 16 ) =126 g
Molarity ,M = (mass / M' ) / Volume in L      0.08   = ( m / 126 ) /0.25            m= 2.52 g

2. If 32.96 mL of a NaOH solution are required to tirate 25.00mL of0.08121 M H2C2O4 to the end point,what is the molarity of the sodium hydroxide solution? NV = N'V' N = normality of NaOH = ? V= Volume of NaOH = 32.96 mL N' = Normality of H2C2O4 =Molarity * basicity = 0.0821 * 2 = 0.1642 N V' = Volume of H2C2O4 = 25mL So, N = 0.1245 N Molarity ,M = Normality / acidity                    = 0.1245 / 1                    = 0.1245 M

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