hemistry student Ana had a chance to look over the results for her entire class. She noticed a trend among the results:The percent error was greater for cases where the percent composition was low. Trial 6 had only 5 copper pennies and the percent error for the precent composition of copper was about 50%. Trial 7 had only 5 zinc pennies and had a percent error of about 80% for the percent composition of zinc pennies. Suggest an explanation for why this might be true. Answer the question that is asked. Regardless of your personal feelings, you have to suggest an explanation for why Ana's statement might be true.

answer; i believe that the correct answer is (a) potassium(k)

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-

the answer is true. hope it .

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