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.

Determining the Molar Volume of a Gas

Measurable Properties of Gases:

A gas is said to be a state of matter which can be differentiated from solid and liquid due to its relatively low density, viscosity, and its ability to contract and expand or diffuse with respect to change in the temperature and pressure. The characteristics of the gases can be described using four important properties, which are collectively termed as called as the measurable properties of gases.

The measurable properties of gases are
1.Volume of the gas
2. Pressure of the gas
3. Temperature of the gas
4. Amount of the gas (mass)

Volume

Volume which is one of the measurable property of the gas is denoted by the letter 'V'. It is expressed in litres(L) , milliliters(mL), cubic centimeters(cm³),  cubic metres(dm³)  and cubic decimetres(dm³).
1litre = 1000 millilitres  , 1 millilitre = 1cubic centimetre and 1 cubic metre = 1000 cubic centimetre
1L  = 1dm³ = 10^–3 m³   = 1000 mL = 1000000 cm³
The volume of the gas depends on the pressure, temperature and the amount of gas present.The measurement of volume of gas requires the measurement of volume of the container in which the gas is present.

Pressure

Pressure is the next important measurable property of the gas which is denoted by the letter 'P'. Pressure of the gas is the force exerted by the gas per unit area.It depends on the kinetic energy of the molecules. As the kinetic energy inturn depends on temperature, the pressure is directly proportional to the temperature of the gas.
Pressure (P) = Force/Area = (Mass) (Acceleration)/Area
Pressure is commonly expressed in atmospheres, mm of Hg, torr, bar, and K.Pa.
1atm = 760mm of Hg = 760 torr = 1.01325 bar = 101.325 kPa = 101.326 x 10³ N m^-2  
Pressure of the gas can be measured by Barometer.    

Temperature

The temperature of the gas is denoted by  the letter 'T'.The temperature of a gas depends on the kinetic energy of the gas.The gases  expand on increasing the temperature.The temperature of the gas is generally expressed in Fahrenheit (F^o), Centigrade degree (^oC)  or celsius degree and Kelvin (K).
   K = ^oC + 273  and ^oC/5 = F^o–32/9
The temperature is measured by the help of a Thermometer.

Amount of gas

Amount of gas or the mass is a measurable property of the gas.The mass of the gas is related to the number of moles of the gas. The mass of the gas is generally expressed in kilograms(Kg) or grams(g).
number of moles (n) = mass of the gas/ molar mass of the gas
                                    n = m/M
The mass of the gas can be found through weighing. The mass of the gas can be obtained by subtracting the mass of the container in which the gas is present from the total mass.

Determining The Molar Volume of a Gas:

The Ideal gas law states that,
PV=nRT
Where P is pressure,V is volume, n is number of moles,R is gas constant and T is temperature.
At STP,which means standard temperature and pressure,the values of  temperature and pressure are 273 K [0 C] and 1 atm respectively.
If these values are substituted,we get,
1xV=nRx273
also substitute n= one mole and substitute value of  R= 0.082 Liter-Atmospheres per Mole-Degree Kelvin,
we get,
V=22.4 L
So one mole of a gas at STP would occupy 22.4L of volume.This is called as molar volume of a gas.
So irrespective of a gas,its one mole would occupy 22.4L of volume.

Illustration on Determining the Molar Volume of a Gas :

Find the volume of 88g of CO₂ at STP.
First find moles of CO_2. in 88g of CO_2.
Moles=Mass in g/Molar mass
=88/44
=2 moles
Volume of 2 moles= 2 x 22.4
=44.8 L
The volume of oxygen gas at STP is 128 L.Find the number of moles.
Now the molar mass of oxygen is 32.
So 32g would ocuupy 22.4 L
128 g would occupy 128 x 22.4 /32
=4 x 22.4
=89.6 L

Determining Molar Volume and the Number of Molecules of Gas

Avogadro further determined that a mole of a gas at STP contains 6.022 x 10²³ molecules.
The determination of the molar volume of 22.4 L and the number of molecules i.e. 6.022 x 10²³  and the number of molecules i.e. 6.022 x 10²³ at STP,brought out a revolution in the study of gases as well as other phases.
Let us consider an example.
Find out the number of molecules in   128g of oxygen gas at pressure 1 atm and temperature 273⁰K.
Let us find the number of moles.
Moles=Mass in g/molar mass
=128/32
=4
Now one mole of a gas contains 6.022 x 10²³
So 4 moles would contain,
4 x 6.022 x 10²³
=24.088 x 10²³ molecules.

Non Uniform Acceleration

Introduction:

Acceleration of a body is defined as the rate of change of its velocity with time. That is, Acceleration=Change in velocity / time taken. Here, the change in velocity means the difference between the final velocity and the initial velocity. A body has a non-uniform acceleration, if its velocity increases by unequal amounts in equal intervals of time or the velocity change takes place at a non-uniform rate.

Non Uniform Acceleration

Nonuniform acceleration represents the mainly common explanation of activity.

 It refers toward difference within the speed of modify in velocity.

Just locate, it way to speeding up vary through motion. This difference is able to be articulated also within expressions of location (x) otherwise time (t).

We recognize, if we are able to illustrate non-uniform quickening within one dimension, we are capable of simply expand ing the study near two or else three dimensions with composition of activity during element path. Thus, we shall detain ourselves toward the thought of non-uniform to be exact changeable speeding up in one dimension.

We shall explain nonuniform acceleration with terms of speed or else acceleration within expressions of moreover of instance, “t”, or else location, “x”.

We shall believe that the  explanation of nonuniform speeding up through convey acceleration within expressions of speed.  As a substance of information, here it is  able to be assorted potential. In addition, nonuniform acceleration might engross understanding acceleration instance or else velocity instant graphs.

Example for Nonuniform Acceleration

The velocity or speed of a car running on the road in a crowded city continuously changes due to the frequent application of brakes. At one moment the velocity increases whereas at another moment it decreases. So, when the moving body has different accelerations at different points of time during its motion, it is said to have non-uniform acceleration or variable acceleration.

Thus, a body has a nonuniform acceleration if its velocity increases by unequal amounts in equal intervals of time or the velocity change takes place at a non-uniform rate.