Which statement describes the appearance of a temperature-vs.-time graph?
A horizontal line shows that the temperature
increases at a constant rate over time.
O. A vertical line shows that the temperature
decreases at a constant rate over time.
Horizontal lines where the temperature is
constant during phase changes connect
upward-sloping lines where the temperature
increases.
Horizontal lines where the temperature
increases are connected by upward-sloping
lines where the temperature is constant for
each phase.

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.

answer: i dont know the answer but this might

explanation:

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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