Do the number of atoms change in a chemical reaction? i will give brainliest

No.

Explanation:

The reason comes the Law of Conservation of Mass.

In an ordinary chemical reaction, you cannot create or destroy atoms.

So, you must have as many atoms at the beginning of a reaction (in the reactants) as at the end (in the products)

We use this principle to balance chemical equations.

For example, the equation for the formation of water from hydrogen and oxygen is

2H₂ + O₂ ⟶ 2H₂O

There are four atoms of H and two of O both before and after the reaction.

answer///carbon;

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