4. This neurotransmitter is a part of the brain's "reward system" (5 Points)
Nicotine
Dopamine
Addiction
Nerves

Dopamine

Explanation:

The regions of the brain comprising the “reward system” use the neurotransmitter dopamine to communicate.

i wish i could but this one is weird give me abc and i can solve it.

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