Oxalic acid dihydrate is a solid, diprotic acid that can be used in the laboratory as a primary standard. Its formula is H2C2O4•2H2O. A student dissolves 0.647 grams of H2C2O4•2H2O in water and titrates the resulting solution with a solution of barium hydroxide of unknown concentration. If 35.9 mL of the barium hydroxide solution are required to neutralize the acid, what is the molarity of the barium hydroxide solution ?

Explanation:

Hello,

In this case, the first step is to compute the oxalic acid dihydrate's moles as shown below, considering its molar mass as 126 g/mol:

Now, since the undergoing chemical reaction is:

Their molar relationship is 1 to 1, therefore:

Thus, the barium hydroxide's molarity turns out:

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answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol