Question 4

the overall enthalpy of a reaction can be determined using hess’s law to add up what quantities?

the enthalpy of formation reactions.

the specific heat of each reactant.

the specific heat of each product.

the heat of vaporization of each reactant.
3 points
question 5

which of these reactions release heat?

socl2(l) + h2o(l) → so2(g) + 2 hcl(g) δh = +10.3 kj

pcl3(l) + 1/2 o2(g) → pocl3(l) δh = -325.7 kj

pcl3(g) + cl2(g) → pcl5(g) δh = -92.5 kj

cl3po(g) → pcl3(g) + 1/2 o2(g) δh = +285.7 kj
4 points
question 6

to calculate the enthalpy of the reaction, n2 (g) + 3h2 (g) → 2nh3 (g), you need to subtract which heats of formation?

n2 (g) and h2 (g)

nh3 (g)

n2 (g), h2 (g), and nh3(g)

none of them
3 points
question 7

using the table below, what is the change in enthalpy for the following reaction when all reactants and products are in the gaseous state?

nitrogen dioxide → nitrogen monoxide + oxygen

substance δhf (kj/mol)
no2 (g) 33.85
no (g) 90.37
o2 (g) 0.0
o3 (g) 142.0

113.0 kj

255.0 kj

56.5 kj

-113.0 kj
3 points
question 8

if all the coefficients of a reaction are multiplied by 1 during a hess’s law calculation, what must be done to the δh for that reaction?

it must be divided by 2.

it must be multiplied by 3.

it must have 1 subtracted from it.

it must be left alone.