The official web site of the nobel prize explains that marie curie’s chemistry prize was partly for her discovery that the radioactivity of a substance is unaffected when it undergoes a chemical reaction. what does this discovery imply?

radioactivity involves all particles that make up an atom.
radioactivity involves the particles that make up an atom’s nucleus.
radioactivity involves only neutrons.
radioactivity involves only the electrons in an atom’s electron cloud.

D) Radioactivity involves only the electrons in an atoms electron cloud

D) Radioactivity involves only the electrons in an atoms electron cloud

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