Hydrogen Fuel Cell Economy

Introduction

Let us discuss about the hydrogen fuel cell economy. The fuel cell is combined with of hydrogen and oxygen. The fuel cell to create the electricity, heat and water. The working electric power energy produced by chemical reaction in hydrogen fuel cell. The cell in which by incineration of gaseous fuel, the incineration effect obtained is changed into electrical effect in single step. Those cells are called as the hydrogen fuel cell economy.

Explanation of Hydrogen Fuel Cell Economy

 The simple explanation of cell utilizing hydrogen fuel cell economy is given in following diagram.
                               
In a vessel two porous carbon disphrams are placed and concentrated aqueous solution of NaOH is filled in between. Both these disphrams work as inert electrodes. The electrode substitute as anode consists of combined powder of platinum and silver oxide as catalyst. When hydrogen gas from the anode and oxygen gas from the cathode are passed the next reactions take place at the electrodes and electric current is formed.
            
      
 Theoretically it can be expected that the efficiency of like this cells may be 100% but in reality the efficiency is about 70-75%. The potential of this cell is about the volt is 1.23. Next we see the advantage of hydrogen fuel cell economy.

Advantages of hydrogen fuel cell economy
There are many advantages of the hydrogen fuel cell economy as compared to other cells. There is no air pollution due to this hydrogen fuel cell economy. It does not produce noise and its efficiency is especially high as compared to electrical production by thermal power station.

           The American scientists used this type of cell in space shuttle during Apollo space program. In addition the steam produced during cell reaction was cooled and used the available water. Recently, use of such hydrogen fuel cell economy is increasing in foreign countries.

Galvanic cell potential

Introduction :

The potential of individual half cell cannot be measured . We can only measure the difference between the two half cell potentials that gives the EMF of the cell. According to convention, a half cell called the standard hydrogen electrode represented by Pt(s)│H₂(g)│H⁺(aq), is assigned a zero potential at all temperatures corresponding to the reaction
            H⁺(aq) + e^- →1/2 H₂(g)

The standard hydrogen electrode consists of a platinum electrode coated with platinum black. The electrode is dipped In an acidic solution and pure hydrogen gas is bubbled through it. The concentration of both the reduced and oxidized forms of hydrogen is maintained at unity. This implies that the pressure of hydrogen gas is one bar and the concentration of hydrogen ion in the solution is one molar. At 298 K the emf of the cell, standard hydrogen electrode || second half cell constructed by taking standard hydrogen electrode as anode and the other half cell as cathode, gives the reduction potential of the other half cell. If the concentrations of the oxidized and reduced form of the species in the right hand half cell are unity, then the cell potential is equal to standard electrode potential, E^-_R of the given half cell.
      E^- = E^-_R – E^-_L
As E^-_L  for standard hydrogen electrode is zero.
      E^- = E^-_R – 0 = E^-_R

Galvanic Cell Potential

Measurement of Galvanic cell potential:

The measured emf of the cell:

 Pt(s) | H₂ (g, 1 bar) | H⁺(aq, 1 M)||Cu²⁺(aq,1M)| Cu

Is 0.34 V and it is also the value for the standard electrode potential of the half cell corresponding to the reaction:

  Cu²⁺ (aq, 1M) + 2e^- →Cu(s)

Similarly, the measured emf of the cell:

Pt(s)│H₂(g, 1 bar)|H⁺(aq, 1M)||Zn²⁺(aq,1M)|Zn

Is -0.76 V corresponding to the standard electrode potential of the half cell reaction:

   Zn²⁺(aq, 1M) + 2e^- →Zn(s)

In view of this convention, the half cell reaction of the daniell cell can be given as:

Left electrode: Zn(s) → Zn²⁺(aq,1M) + 2e^-

Right electrode: Cu²⁺(aq, 1M) + 2e^- →Cu(s)

The overall reaction of the cell is the sum of the above two reactions and we obtain the equation:

Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

Emf of the cell = E⁰_cell = E⁰_R – E⁰_L

                                        = 0.34 – (-0.76) = 1.10 V

Summary of Galvanic Cell Potential

The Emf of galvanic cell potential is 1.10 V.

Hydrogen Oxygen Fuel Cell

Introduction 

Production of electricity by thermal plants is not a very efficient method and is a major source of pollution. In such plants, the chemical energy (heat of combustion) of fossil fuels (coal, gas or oil) is first used for converting water into high pressure steam. This is then used to run a turbine to produce electricity. A galvanic cell directly converts chemical energy into electricity and is highly efficient.  Galvanic cells are designed to convert the energy of combustion of fuels like hydrogen, methane, methanol, etc. directly into electrical energy are called fuel cells. It consists of an anode, cathode, catalysts and most often an electrolyte.  Fuel cells are different from batteries in that they consume reactant from an external source, which must be replenished.

Hydrogen Oxygen Fuel Cell and its Working Principle

It is one of the most successful fuel cell which uses the reaction of hydrogen with oxygen to form water. Hydrogen oxygen fuel cell was used for providing electrical power in the Apollo space programme. The water vapour produced during the reaction were condensed and added to the drinking water supply for the astronauts.  In the cell, hydrogen and oxygen are bubbled through porous carbon electrodes into concentrated aqueous sodium hydroxide solution. Catalysts like, finely divided platinum or palladium metals are incorporated into the electrodes for increasing the rate of electrode reactions.
Catalysis plays a very important role in Hydrogen oxygen fuel cell, separating the electrons and protons of the reactant fuel (at the anode), and forcing the electrons to travel though a circuit, generating electrical power.  At the cathode, another catalytic process takes the electrons back in, combining them with the protons, which have traveled across the electrolyte and the oxidant to form waste products (like carbon dioxide and water).

The electrode reactions of Hydrogen oxygen fuel cell are given below:
Reaction at Cathode:  O2 (g) + 2H₂ O(l ) + 4e⁺    4OH^–(aq)
Reaction at Anode:     2H₂ (g) + 4OH^–(aq)          4H₂O(l) + 4e^–
Overall reaction is:
2H₂(g) + O₂(g)         2 H₂O(l )
The cell runs continuously as long as the reactants are supplied. Fuel cells produce electricity with an efficiency of about 70 % compared to thermal plants whose efficiency is about 40%.

Applications of Hydrogen Oxygen Fuel Cell

Hydrogen oxygen fuel cells are used in wide range of applications, from producing electricity for the grid to powering portable devices, like lap tops. It is also been used in automobiles on an experimental basis as fuel cells are pollution free with high efficiency.

Sodium Bromide Chemical

Introduction :

The other name so sodium bromide is sedoneural. It belongs to family of salts. It resembles sodium chloride and has a white crystalline structure. It is odorless. This is an important source for bromide ion. NaBr is the chemical formula of sodium bromide. It is completely soluble in water and exhibits partial solubility in acids. It has resemblance to sodium chloride.

Chemical Reactions & Uses of Sodium Bromide:

Alkyl chlorides are converted to alkyl bromides using NaBr. This is called Finkelstein reaction.
NaBr + RCl `|->` RBr + NaCl

Chemical reaction of Sodium bromide with chlorine:

In organic synthesis, NaBr is commonly utilized as a source for bromide nucleophile which converts alkyl chlorides into more reactive alkyl bromides using Finkelstein reaction.
NaBr + RCl → RBr + NaCl
As Sodium chloride is utilized as the source for bromine. This is done when chlorine gas is bubbled via with the sodium bromide’s aqueous solution. It is a source of HBr, sodium bromide and it is treated with a very non volatile and strong acid.
NaBr + H₃PO₄ → HBr + NaH₂PO₄

While chlorine water is poured to the sodium bromide solution, the chlorine water oxidizes the bromide ion to bromine that is a liquid or vapor of brown color. Likewise, bromine oxidizes iodide to form iodine which is violet colored solid. All depends on concentrations. Depending on this, the bromine and chlorine can separate from the solution, but only one aqueous layer will be there. Both of the reactions are the good example of oxidation-reduction reaction. It is also known as redox reaction.

Applications of reaction of Sodium bromide with chlorine

It is used as an anticonvulsant, hypnotic, and as a sedative in the medicines. As a source for bromide ion (pharmacologically active), it is similar to potassium bromide.

This also comes to use in photography.

To create a bromide ion that is reserved in bromine spa which is antimicrobial treatment.

Precautions necassary during reaction of Sodium bromide with chlorine:

As sodium bromide proves to be harmful if it is inhaled or swallowed in a large amount, it affects the brain, central nervous system and the eyes. This chemical compound may irritate the eyes, skin, and the respiratory system.

When NaBr is treated with a non-volatile acid like H₃PO₄ hydrogen bromide is produced.
NaBr  +  H₃PO₄   `->`    HBr + NaH₂PO₄
It has a molecular weight of 102.89. 755 degree Celsius happens to be its melting point. 1390 degree Celsius is supposed to be its boiling point. 3.21 is its specific gravity. Its solubility is 116g/100g of water.
Production of sodium bromide is very costly. Therefore sodium halide is formed by reacting sodium metal with halogens and then burnt with bromine to produce sodium bromide
Photographic industry uses Sodium Bromide for its processing. It is also used as intermediate chemical for manufacture of various other chemicals. Water clarification is also one of its application. It is also used as a sedative in pharmaceutical industry. It is used in spa industry as sanitizers of hot water tub.
NaBr affects nervous system and brain if exposed to large quantities. It has irritability character and hence will cause irritation to skin as well as eyes. Therefore, one needs to wear gloves or other protective gear to protect their skin. When exposed to long durations it can cause memory loss, skin rashes etc.
NaBr  requires cool place for storage. Containers, which store these compounds when empties needs to be destroyed, as they are dangerous. NaBr is not supposed to be an explosive hazard. Incompatibilities like acids, oxides etc needs to be avoided

Conclusion on Sodium Bromide Chemical:

Sodium bromide with so many uses is a boon to chemical community. However, due to hazardous nature it needs to be handled carefully.

Physiological Properties of Water

Introduction:

Water constitutes around 70% of the earth’s surface being the most abundant compound that is available on the planet. It is often referred to as a universal solvent as many substances tend to dissolve in water. In the figure below, we can see the molecular binding of water molecules.Water in our body plays a major role in performing various function which are important for day to day activities that carries inside the body. Physiological properties deals with the functioning of water inside the tissues and the organs.Let us discuss in brief.

The Physiological Properties of Water

• Water makes up most of the body's weight.
• It carries helps in transporting of substances inside body cells with the circulatory system.
• It helps in excretion. The waste materials present inside the body can be removed by filtration through kidneys. Water plays an important role in excreting out these toxic materials.
• It helps the cells to gain dissolved oxygen.
• It helps when the body gets dehydrated.
• Our skin contains water. During any disease, when the water content inside the body is affected, hormones like ADH, aldosterone helps in regulating the water content of the body.
• Water gets inside our body through stomach, intestinal canal, then it reaches the blood and the volume gets increased and which in fact raises the vessels of circulatory system. Water makes the blood dilute and hence the circulation becomes fast.
• It is excreted or expelled by skin, lungs, kidneys, and intestines.  Due to solvent action, it helps in dissolving  a variety of poisonous products of  tissues.
• It helps in urinary excretion where the waste material urea is excreted, which is formed by kidney.
• We should drink a lot of water that produces copious perspiration along with urinary excretion.
• It also helps in preventing constipation problems related to improper bowel movement.

Conclusion for the Physiological Properties of Water

From the discussion on the psychological properties of water, we conclude that water is an essential substance for life on the planet earth as it not only makes up 55-78% of the human body but also is very important source of life to plants and animals. We also came across the importance of water inside our body cells.

Properties of Aqueous Acids

Introduction 

Solution in which the solvent is water is an aqueous solution. In chemical equations it is represented by appending (aq) to the relevant formula. The other synonyms of aqueous are similar to , pertaining to, related to, or dissolved in water. In chemistry water is the omnipresent solvent as it is an excellent solvent as well as it is available in abundance in nature.

Properties of Aqueous Acids

• Aqueous acids has a sour taste
• Acids strong in nature and high in concentrations are responsible for harsh or strong feeling on noses
• To indicators it reacts turning methyl orange  & blue litmus red, color of phenolphthalein does not change
• Hydrogen & metal salt is produced on reaction with metals
• Produces water, salt & CO₂ on reaction with metal carbonates.

       Let us take an example as

NaOH + HCl   `->` NaCl + H₂O

In the above reaction, the H⁺ from aqueous acid HCl and the OH^- from the base NaOH, reacts to produce water molecule.Infact this reaction is also termed as neutralization reaction, as an aqueous acid acts upon with a base to produce or to give water and salt.

• Water & salt is produced on reaction with a base
• Produces water and a salt on reaction with metal oxide
• Depending on the dissociation (degree) will conduct electricity
• Hydronium (H₃O+) ions (solvonium ions) are produced in water
• Responsible for denaturing proteins

Reaction of Acid and Water

Common aqueous acids, from weakest to strongest are acetic acid (CH₃COOH) , carbonic acid (H₂CO₃) , hydrochloric acid (HCl).

H₂O + HCl `->` H₃O⁺+ Cl^-

In dilute water solutions of strong acids like perchloric, hydrochloric and sulfuric, act essentially as solutions of H₃O⁺  ions and the acidity gains in relation to the concentration. At greater concentrations, more than one molar (which is, one mole acid for each litre of the solution), yet, the acidity, as considered or measured by the action on catalytic ability or the indicators, increases much quickly than the given concentration. For an example, if we consider 10 molar solution of some strong acid, then it is about 1,000 times as acidic as a 1 molar solution.

Conclusion for of Aqueous Acids

From the discussion, we conclude that aqueous acids play an important role in laboratory experiments and research and they have unique properties as listed above.

Pressure Volume Temperature Relationship

Gas molecules are in constant motion.In a container the number of molecules are colliding with the walls of the container.This creates pressure.The gas molecules also occupy certain space.This is volume.

Introduction to pressure volume temperature relationship

Out of three phases of a substance i.e solid ,liquid and gas,only the gas phase exhibits the properties of pressure and volume distinctively that their correlation could be developed.

• Boyle was the first person to study and establish the correlation between pressure and volume of a gas.He noticed that ,at constant temperature,the volume of a gas varies inversely with the pressure.In a container,if the pressure on the gas is increased,the gas gets suppressed,in turn reducing the volume.So more the pressure,less the volume.He put it as under,

At constant temperature,
P=k / V  where k is constant.

Charles' Law Shows Relationship between Volume and Temperature

• Charles developed equation to find the relationship between the temperature and volume.

It says that at constant pressure,the volume of a gas is directly proportional to the temperature.
Hence,
V `alpha`
V=kT

Universal Gas Law and Ideal Gas Law Shows Relationship between Pressure Volume and Temperature

• Boyle's and Charles's law when combined,give us universal gas law,

 P1V1/T1=P2V2/T2
What is the presure at 200k ,volume 1 L, if at 1 atm and 300k the volume is 2 l.?
P1V1/T1=P2V2/T2
1 x 2/300=P₂ x 2/200
P2= 0.666 atm
This is the correlation between pressure ,volume and temperature.It is very useful in determining the value of any of the missing parameter if the other are known.

• Further more detail attempts were made and this correlation could be found for given number of quantity of a gas.Therefore,for a given number of moles of a gas,

PV=nRT

where n is number of moles of a gas,R is gas constant and T is temperature.This is the ideal gas law.
It may be remembered here that all this laws are meant to be in ideal conditions.In practice there always will be deviation.
Avogadro's number gives us relation between the number of moles/number of molecules and the volume.Thus from the above equation,pressure,or volume of a gas can be calculated if either of the number of moles/number of molecules is known.