(Forgot to ask this question last time) Which is true about molecules?
A. A molecule is two or more atoms joined
together.
B. A molecule is two or more protons joined
together.
C. A molecule is two or more neutrons bonded
together.

A is the correct answer.

може ли да зареждате повече информация, моля

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