# 10.4 Phase diagrams  (Page 3/9)

 Page 3 / 9

## Determining the state of carbon dioxide

Using the phase diagram for carbon dioxide shown in [link] , determine the state of CO 2 at the following temperatures and pressures:

(a) −30 °C and 2000 kPa

(b) −60 °C and 1000 kPa

(c) −60 °C and 100 kPa

(d) 20 °C and 1500 kPa

(e) 0 °C and 100 kPa

(f) 20 °C and 100 kPa

## Solution

Using the phase diagram for carbon dioxide provided, we can determine that the state of CO 2 at each temperature and pressure given are as follows: (a) liquid; (b) solid; (c) gas; (d) liquid; (e) gas; (f) gas.

Determine the phase changes carbon dioxide undergoes when its temperature is varied, thus holding its pressure constant at 1500 kPa? At 500 kPa? At what approximate temperatures do these phase changes occur?

at 1500 kPa: $\text{s}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{l}$ at −45 °C, $\text{l}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{g}$ at −10 °C;

at 500 kPa: $\text{s}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{g}$ at −58 °C

## Supercritical fluids

If we place a sample of water in a sealed container at 25 °C, remove the air, and let the vaporization-condensation equilibrium establish itself, we are left with a mixture of liquid water and water vapor at a pressure of 0.03 atm. A distinct boundary between the more dense liquid and the less dense gas is clearly observed. As we increase the temperature, the pressure of the water vapor increases, as described by the liquid-gas curve in the phase diagram for water ( [link] ), and a two-phase equilibrium of liquid and gaseous phases remains. At a temperature of 374 °C, the vapor pressure has risen to 218 atm, and any further increase in temperature results in the disappearance of the boundary between liquid and vapor phases. All of the water in the container is now present in a single phase whose physical properties are intermediate between those of the gaseous and liquid states. This phase of matter is called a supercritical fluid    , and the temperature and pressure above which this phase exists is the critical point    ( [link] ). Above its critical temperature, a gas cannot be liquefied no matter how much pressure is applied. The pressure required to liquefy a gas at its critical temperature is called the critical pressure. The critical temperatures and critical pressures of some common substances are given in [link] .

Substance Critical Temperature (K) Critical Pressure (atm)
hydrogen 33.2 12.8
nitrogen 126.0 33.5
oxygen 154.3 49.7
carbon dioxide 304.2 73.0
ammonia 405.5 111.5
sulfur dioxide 430.3 77.7
water 647.1 217.7

who is the father of chemistry
what is hybridization and bonding
please who is the father of chemistry
Naomi
Antoine Lavoisier
Abdelkarim
Abdelkarim
Also, god has created everything
Abdelkarim
(Allah, the creator)
Abdelkarim
how to determine the empirical formula
what is neutralisation reaction
It is a reaction where an acid (aq) reacts with an alkali (aq) to form salt AND water.
Abdelkarim
What is the ratio of the average kinetic energy of a SO 2 molecule to that of an O 2 molecule in a mixture of two gases? What is the ratio of the root mean square speeds, u rms , of the two gases?
what is methyl orange
its an indicator
Abigail
It is an organic molecule that reacts with acid/base medium and shows change in colour (due to formed products). It can be used to test for alcohols which are prohibited to drink in Islam as it is bad for brain and liver and immunity.
Abdelkarim
it is an indicator used to determine the end point in an acid-base titration
xMah_Bx
Abdelkarim
covalent bond explanation
God has lictured these rules that the electrons move with them and the space time curve. So we prwy to God in Islam or we suffer. Please learn about Islam and science and mention God and thank him.
Abdelkarim
yes, it is very true. God is the one who inspires science. Then we, as his children, have the privilege to learn about what he has created. I'm still a novis at chemistry. I still have a lot to learn.
Eric
Beautiful, however, what I learned from the Quran is that god has created human and has a mission like managing the ecology, building, learning, mentioning god (saying glory to Almighty for instance few times and periodic). And the moat important prayer lile prophet Muhammed the last meassenger.
Abdelkarim
Also God forgives all sins except assossiating any one with him like sons and daughters or stone sculpture. Beautifully, if some one stops from saying this God can switch their sins to virtueness. And God all merciful doesnt get bored forgiving people who ask for forgiveness.
Abdelkarim
Also, there is a versw in the Quran that sates: { corruption has appeared in the land and the sea he will taste them from what their hands have gained} this reminds me of covid from stupid politicians who will be throne to hell.
Abdelkarim
nature of bond in N2 molecule is
Triple covalent bond, and that is why it is hardly reactive because in order to react you must break three strong covalent bonds.
Abdelkarim
what is electromagnetic energy
in a school of 120 students, 41studied mathematics, 48studied chemistry and 42 studied physics, 16 studied both chemistry and mathematics, 14 studied mathematics and physics, 18 studied chemistry and physics and 9 studied all the three subjects. how many of them studied exactly one subject?
Does Chromium oxidize?
yes
Alaa
@Alaa It doesn't.
Jag
yes. it's a very strong oxidizing agent
xMah_Bx
what is compound
what are the types of hydrocarbon
homologous series is under what
Dolapo
Jag
OK Aliphatic and Aromatic.
Jag
What is an acid
What is hydro carbon
Progress
A hydro carbon is an organic compund formed of carbon and hydrogen only that comes from plant derivatives. It is mercy from God as it has lots of benifits. In Islam, we know from the Quran that God has created for every illness a cure. We sometimes find such compunds in plants and we use it in pills
Abdelkarim
what are the types of hydrocarbon
Dolapo
we have two types of hydrocarbons Aliphatic and Aromatic
Dr
under Aliphatic we have Alkane, Alkene,Alkyl Aromatic we have Benzene
Dr