Astudent weighs a sample of potassium hydrogen phthalate (khp) to prepare a primary standard for a titration. she later discovers that the khp was contaminated with sugar. to determine the amount of khp in the mixture, she takes 5.368 g5.368 g of the mixture and make a 100.0 ml100.0 ml solution. the student then titrates 10.00 ml10.00 ml of this solution with a 0.1224 m0.1224 m sodium hydroxide solution. she finds that 16.74 ml16.74 ml of the naoh naoh solution is needed to reach the end point. what is the percent by mass of khp in the mixture

2b2t

explanation:

2b2t

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

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.