# Question #3a2df

##### 1 Answer

#### Answer:

Here's what I got.

#### Explanation:

Once again, start by making sure that you understand what **enthalpy of sublimation** means.

For a given substance, its *enthalpy of sublimation* tells you how much heat is **needed** in order for a *solid* *vapor* phase change to take place.

Now, the *molar enthalpy of sublimation* tells you how much heat is needed in order to convert **one mole** of a substance from solid to vapor **at a specific temperature** and **at a specific pressure**.

Now, carbon dioxide's *normal sublimation point* occurs at a pressure of

The thing here is that the *enthalpy of sublimation* for carbon dioxide at its normal sublimation point is equal to **not** to

https://en.wikipedia.org/wiki/Dry_ice

So my guess is that the value given to you is *incorrect*. I will use the correct value in my calculations, and leave it up to use to redo them using the given value.

So, you know that you need **one mole** of carbon dioxide from *solid* at its normal sublimation point to *vapor* at its normal sublimation point.

This means that all you have to do here is figure out how many *moles* of carbon dioxide you have in that

#2.0 * 10^(3) color(red)(cancel(color(black)("g"))) * "1 mole CO"_2/(44.01color(red)(cancel(color(black)("g")))) = "45.44 moles CO"_2#

It follows that

#45.44 color(red)(cancel(color(black)("moles CO"_2))) * "25.2 kJ"/(1color(red)(cancel(color(black)("mole CO"_2)))) = "1145.1 kJ"#

Rounded to two sig figs, the number of sig figs you have for the mass of carbon dioxide, the answer will be

#q = color(green)("1100 kJ")#