Check all of the boxes that are true about the electron: it is outside the nucleus
it has a positive charge
it has no mass
it has a negative charge
it is inside the nucleus
it is the same as the atomic number
it is the same as the number of neutrons

1,4,6,7

Explanation:

Electrons have a negitive charge and are outside of the nucleus and have the same atomic number and have the same number os nutrons.

no but i do not usually comment or use my voice that much when it comes to social media

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