Which branch science consist of?
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Modern science is typically divided into three major branches that consist of the natural sciences (biology, chemistry, physics, astronomy and Earth science), which study nature in the broadest sense; the social sciences (e.g. psychology, sociology, economics, history) which study people and societies; and the formal ...

Explanation:

The four major branches of science are, Mathematics and logic, biological science, physical science and social science. The first branch is mathematics & logic.

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