The properties of carbon dioxide gas

The properties of carbon dioxide gas

Do you know that carbon dioxide gas is produced from the breathing of humans and animals , It is produced from the combustion of coal or hydrocarbons , the fermentation of liquids , and  It is a colorless , tasteless and odorless gas .

You must know that carbon dioxide gas ( CO2 ) one of the most stable of all molecules as it consists  of a single carbon atom covalently bonded to two atoms of oxygen , and this bond is very strong , and it is a gas at standard temperature and pressure .

 

Carbon dioxide gas

We have to know that carbon dioxide gas can change the pH of water and it dissolves slightly in the water to form a weak acid called carbonic acid , and it is a greenhouse gas as it transmits visible light but it  absorbs strongly in the infrared and near-infrared .

You have to know that most carbon dioxide units are slightly acidic by nature , the level of acidity can be modified by dissolving the molecules in the  water , it is soluble in  ethanol and in acetone , It is easily dissolves in the water , so it is not collected by the displacement of water  .

Everybody should know that carbon dioxide gas reacts with alkalis to give carbonates and bicarbonates , it is a linear covalent molecule , it is an acidic oxide , and it reacts with the water to give carbonic acid .

Everybody must know that carbon dioxide gas reacts with magnesium to form magnesium oxide ( white powder ) and carbon or coal ( black substance ) that deposits on the wall of the cylinder .

Everyone have to know that carbon dioxide gas does not burn and does not help in burning , so it is used in extinguishing the fires , and it is heavier than the air , so it is collected by upward displacement of air .

You have to know that carbon dioxide gas is prepared by adding dilute hydrochloric acid to calcium carbonate , it is prepared by upward displacement of air because it is heavier than the air , and it is not collected by displacement of water as it easily dissolves in the water , and it is also prepared by adding lemon juice or vinegar to sodium bicarbonate ( the backing powder ) .

 

Carbon dioxide gas properties .

You have to know that carbon dioxide gas forms a solid substance at temperatures below -70 degrees Celsius ( -94° Fahrenheit ) , It may also transform into a liquid when it is dissolved in the water under constant pressure , it is very stable , and it is largely unaffected as it interacts with many other materials in the atmosphere .

Everyone should know that  when we inhale carbon dioxide gas  at concentrations much higher than the usual atmospheric levels , it can produce a sour taste in the mouth and a stinging sensation in the nose and throat , as carbon dioxide gas dissolves in the mucous membranes and saliva , and it forms a weak solution of carbonic acid .

Do you know that  carbon dioxide gas molecule is moderately reactive and is non-flammable ? but it will support the combustion of metals such as magnesium , it contains  two double bonds and it has a linear shape , It has no electrical dipole , and  it is fully oxidized .

The properties of carbon dioxide gas

Properties of saturated liquid Carbon Dioxide - CO₂ - density, specific heat capacity, kinematic viscosity, thermal conductivity and Prandtl number can be found in the table below

Temperature - T - (oC)	Density - ρ - (kg/m3)	Specific Heat - cp - (103 J/kg K)	Thermal Conductivity - k - (W/m K)	Kinematic Viscosity - ν - (10-6 m2/s)	Prandtl Number - Pr -
-50	1156	1.84	0.086	0.119	2.96
-40	1118	1.88	0.101	0.118	2.46
-30	1077	1.97	0.112	0.117	2.22
-20	1032	2.05	0.115	0.115	2.12
-10	983	2.18	0.110	0.113	2.20
0	927	2.47	0.105	0.108	2.38
10	860	3.14	0.097	0.101	2.80
20	773	5.0	0.087	0.091	4.10
30	598	36.4	0.070	0.080	28.7

• 1 kg/m³ =  0.0624 lb/ft³ 
• 1 J/(kg K) = 2.389x10^-4 kcal/(kg ^oC) = 2.389x10^-4 Btu/(lb_m ^oF)
• 1 W/(m K) = 0.85984 kcal/(h m ^oC) = 0.5779 Btu/(ft h ^oF) = 0.048 Btu/(in h ^oF)
• 1 m²/s = 10⁴ St = 10⁶ cSt = 10.764 ft²/s= 38750 ft²/h

Carbon dioxide gas is produced from the combustion of coal or hydrocarbons, by fermentation of liquids and the breathing of humans and animals, and by volcanoes.

Carbon dioxide is at a low concentration in the atmosphere and acts as a greenhouse gas. Carbon dioxide is used by plants to produce carbohydrates. The photosynthesis process releases oxygen to the atmosphere.

Carbon dioxide gas is colorless and heavier than air and has a slightly irritating odor.

Freezing point is -78.5 ^oC where it forms carbon dioxide snow or dry ice.

Solubility of CO₂ in Water

To calculate the CO₂ emission from a fuel the carbon content of the fuel must be multiplied with the ratio of molecular weight CO₂ (44) to the molecular weight Carbon 12 -> 44 / 12 = 3.7

Carbon Dioxide emission can be calculated as

q_CO2 = c_f / h_f  C_CO2/C_m         (1)

where

q_CO2 = specific CO₂ emission (CO₂/kWh)

c_f = specific carbon content in the fuel (kg_C/kg_fuel)

h_f = specific energy content (kWh/kg_fuel)

C_m = specific mass Carbon (kg/mol Carbon)

C_CO2 = specific  mass Carbon Dioxide (kg/mol CO₂)

Emission of Carbon Dioxide - CO₂ - when combustion some common fuels are indicated in the table below.

Note! Heat loss - 55-75% - in power generation is not included in the numbers.   

Fuel	Specific Carbon Content (kgC/kgfuel)	Specific Energy Content (kWh/kgfuel)	Specific CO2 Emission (kgCO2 /kgfuel)	Specific CO2 Emission (kgCO2/kWh)
Coal (bituminous/anthracite)	0.75	7.5	2.3	0.37
Gasoline	0.9	12.5	3.3	0.27
Light Oil	0.7	11.7	2.6	0.26
Diesel	0.86	11.8	3.2	0.24
LPG - Liquid Petroleum Gas	0.82	12.3	3.0	0.24
Natural Gas, Methane	0.75	12	2.8	0.23
Crude Oil				0.26
Kerosene				0.26
Wood 1)				0.39
Peat 1)				0.38
Lignite				0.36
Bio energy	0	-		02)

¹⁾ Commonly viewed as a Bio fuel

²⁾ Bio Energy is produced from biomass derived from any renewable organic plant, including

• dedicated energy crops and trees
• agricultural food and feed crops
• agricultural crop wastes and residues
• wood wastes
• aquatic plants
• animal wastes
• municipal wastes and other waste materials

Emissions of CO₂ can contribute to climate change. Combustion of bio energy don't add to the total emission of carbon dioxide as long as the burned bio mass don't exceed the renewed production. (Emission of CO₂ when combusting wood is in reality approximately 0.18 kg/kWh)

A variety of bio fuels can be made from biomass resources, including

• ethanol
• methanol
• biodiesel
• Fischer-Tropsch diesel
• gaseous fuels like hydrogen or methane

Since CO₂ is exhaled by people at predictable levels the content of Carbon Dioxide - CO₂ - in air may be a significant indication of air quality.
A measure of CO₂ indicates the amount of fresh air supply:

• 15 cfm ventilation rate per occupant corresponds to 1000 ppm CO₂
• 20 cfm ventilation rate per occupant corresponds to 800 ppm CO₂

Normal CO₂ Levels

The effects of increased CO₂ levels on adults at good health can be summarized:

•  normal outdoor level: 350 - 450 ppm
• acceptable levels: < 600 ppm
• complaints of stiffness and odors: 600 - 1000 ppm
• ASHRAE and OSHA standards: 1000 ppm
• general drowsiness: 1000 - 2500 ppm
• adverse health effects expected: 2500 - 5000 ppm
• maximum allowed concentration within a 8 hour working period: 5000 ppm  

The levels above are quite normal and maximum levels may occasionally happen from time to time.

Extreme and Dangerous CO₂ Levels

• slightly intoxicating, breathing and pulse rate increase, nausea: 30,000 ppm
• above plus headaches and sight impairment: 50,000 ppm
• unconscious, further exposure death: 100,000 ppm

·         The carbon dioxide - CO₂ - concentration in a room with people can be used as an indication of the ventilation systems efficiency. It's even possible to modulate the ventilation system capacity to the number of people and their activity by measuring the carbon dioxide concentration in the air.

·         The carbon dioxide emission from persons and their activity:

Activity	Respiration per Person (m3/h)	Carbon Dioxide Emission per Person (m3/h)
Sleep	0.3	0.013
Resting or low activity work	0.5	0.02
Normal work	2 - 3	0.08 - 0.13
Hard work	7 - 8	0.33 - 0.38

·         Example - Carbon Dioxide Emission in a Cinema

·         In a cinema with 100 persons at low to normal activity the emission of carbon dioxide will be in the range of 0.02 to 0.08 m³/h per person.

·         The total emission will be in the range of 2 to 8 m³/h.

Carbon Dioxide Concentration in Rooms

The carbon dioxide concentration in rooms can be used to indicate air quality and ventilation system efficiency