The amount of matter in a given space or volume

i'm not sure but i think

Explanation:

matterAnything that has mass and occupies space.

densityThe amount of matter in a given volume of space.

formula for densitymass divided by volume

physical propertyA property of matter that can be observed and measured, without changing its identity.

I hope it helps

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