DATE: A cooling curve is the opposite of a heating curve.
It shows how the temperature of a substance
changes with time, as it is cooled from a gas to a
solid. Here is the cooling curve for one substance:
gas
Temperature / °C
78
liquid
no
JOTOqid
to be
04
-15-
1
solid
Time
Bib 25
a What is the state of the substance at room
temperature (20 °C)?
b Use the list of melting and boiling points on
page 9 to identify the substance.
c Sketch a cooling curve for pure water. d
10​

it takes on an electronical energy

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

b.false that your answer