A student is writing a formula for a compound. What must the student always remember to include? a. At least one number written large as a coefficient

b. At least two lowercase letters

c. Each element must be represented with a capital letter

d. At least one number written low as a subscript

PLEASE HELP!!

the correct answer is:

a. formation of precipitation

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