It takes 48 minutes for 7 people to paint 7 walls. how many minutes does it take 20 people to paint 20 walks?

Explanation:

It will always take 48 minutes. Even if it was one thousand people to paint one thousand walls.

The point here is that it takes 48 minutes for one person to paint one wall. As long as the number of people is the same as the number of walls, it will always take 48 minutes.

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