A1.2516 gram sample of a mixture of caco3 and na2so4 was analyzed by dissolving the sample and completely precipitating the ca as cac2o4.the cac2o4 was dissolved in sulfuric acid and the resulting h2c2o4 was titrated with a standard kmno4 solution. the titration required 35.62 milliliters of 0.1092 m kmno4.calculate the number the number of moles of h2c2o4 that reacted with the kmno4.calculate the number of moles of caco3 in the original sample. calculate the percentage by weight of caco3 in the original sample.

answer: -

reaction:

na + cl ⇌ nacl

balanced chemical equation:

na + 2cl ⇌ nacl2

sodium + clorine goes to form sodium chloride (table salt).

the product is nacl2.

and the reactants are na and cl.

(note: if you don’t know what ⇌ means, read below: -

⇌(double head arrow) means reversible reaction).

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

50.23 i believe is correct but don't quote me on that.