A0.7011-g mixture of sodium chloride and sodium nitrate is completely dissolved in water. when silver nitrate is added to the solution, 0.9805 g of solid precipitate. what is the percent by mass of chloride in the initial mixture?

34.59 %

Explanation:

Sodium chloride dissolves in water as follows:

Chloride ions are then precipitated with silver ions:

Now we use the give mass of AgCl to calculate the moles of Cl:

mol AgCl = mol Cl

Finally we calculate the mass percent of Cl in the initial mixture:

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