Distillation

 Distillation  is a process of separating the components on the basis of their volatility. Higher volatile component will be in vapour phase while less volatile component will remain in liquid phase. 

At a temperature the liquid and vapour phase will achieve equilibrium. When the temperature changes the composition of liquid and gas phase changes. In distilation column the temperature increases from top to bottom, so do the composition of components. At low temperature higher volatile component composition will be more in vapour phase and at high temperature less volatile component will be more in liquid phase. As many trays are there in Distillation column, as no. of equilibrium stages will be.

Reboiler at the bottom of distillation column keeps the temperature high in distillation column while the condenser at top keeps the temperature low.

We can reduce electricity consumption of AC

 In summer the air is very hot and dry. The temperature  of  the  air can be reduced either by desert cooler or AC. Can we use the both? The desert cooler works on evaporative cooling and decreases the temperature very cost effectively, but it also increases the humidity which causes uncomfortable. The humidity will be decreased by AC. So, here Cooler does the cooling and AC does the humidity control. Therefore, by using the combination of desert cooler and AC the cooling gets faster and cost effectively.

Why salt is added to make ice cream

 Adding salt decreases the freezing point of ice. We know pure ice melts at 0°C and if we add salt to it it starts melting at a lower temperature, let's say at -6°C. That means ice start melting at a faster rate than pure ice. That is why it is used in melting snow at roads. But do you wonder how is it helpful in freezing ice cream?

The answer lies in the huge difference in latent heat of melting and specific heat. The latent heat of fusion of ice is approx. 334 KJ/Kg while the specific heat of ice is 2.09 KJ/Kg°C. Let's consider an example, if we have 1 kg of an ice at -10°C. It will absorb 20.9 KJ heat from surrounding and start melting at 0°C. But if we add salt 100 gm of salt to 1 Kg of ice it will approximately decrease the freezing point to -6°C. So it will absorb 8.36 KJ of heat and reaches to -6°C and then start absorbing 334 KJ heat to melt. This means the temperature will be -6°C for quite long time and it will help infreezing ice cream.

Vibration

 VIBRATION

HAV is expanded as hand-arm vibration-exposure of occupational vibration is possible with such tools which create vibration that includes hydraulic, pneumatic, electric, and hand tools powered by gasoline. Hand-arm vibration syndrome (HAVS) is exposure to fingers and hands; a generally irreversible condition is called as HAVS.

EFFECTS-

HAVS is disorder as cumulative trauma and it can be known when one feel numbness in fingers or he may have tingling too. Primarily, it results in damage to blood vessels and nerves of hand resulting in skin blanching (white finger) on use of exposure to cold, together with pain, pins and needles, numbness and loss of manual dexterity. These symptoms are many times taken as frostbite when workers do not know properly. If you smoke you are at increased risk since smoking reduces supply of oxygenated blood to your hands and fingers. main way to prevent Vibration White Finger is to reduce levels of vibration by careful selection of equipment, introduction of damping techniques on existing equipment if practicable, use of alternative work procedures if possible, and to minimize time working with vibrating machinery by job rotation.

Control:

• Wear adequate clothing to keep dry and maintain hand and body temperature at an acceptable level, wear suitable gloves to keep your hands warm. Anti vibration gloves are available which can reduce exposure.

·   Let the machine do the work and grip the handle as lightly as possible, providing that this is consistent with safe working practice.

• Do not use blunt tools. Keep steels sharp and use the appropriate tool for the job. • If you smoke and use vibratory equipment you are at increased risk of vibration related disease, since nicotine reduces the blood supply to the hands and fingers.

• Should attacks of white or blue finger or long periods of tingling and/or numbness occur, report this to your Supervisor, Magnitude of HAV is quantified as acceleration rate in as meters per second squared (m/s2). This is an engineering unit. It should be matter of concern when one exposed to HAV and it occurs within definite frequency range i.e. nominally 5.6Hz to 1400Hz as identified in ISO 5349.

A Simple way to get clean air inside home

As in north India air pollution is a very big problem in starting of winter every year. To get clean air, we have to depend on wind and rain. One way we can reduce the particulate matter by using desert cooler. as the air in room will come in contact with water,the particulate matter gets absorbed in water and the air will be cleaned to some extent.

Effect on Melting Point of Ice: Melting of snow and making of ice-cream

The normal melting point of ice is 0°C i.e. at atmospheric pressure. When the pressure is increased, the melting point of ice decreases. like if if we press the ice it starts melting, this property is used by snow skiers, they press the snow to liquify it which act as lubricant.

The melting point also changes with adding impurities. When salt is added to water the melting point decreases below 0°C i.e. depression in freezing point. This property is used in melting of snow, as well as making of ice. How?

During snow fall, when salt is sprayed to snow the melting point decreases. In case of NaCl, the melting point (freezing point) changes to -7°C i.e. ice will start melting at a temperature of -7°C.

If surrounding temperature is -2°C, the snow (pure water) will remain in solid form but if salt is added, then it will melt.

The same principle is used while making ice cream or used for chilling the ice-cream.

the temperature of pure ice (let's say -10°) will increase rapidly to 0°C as less specific heat and it will become constant at 0°C till all the ice melt. So, this can't be used to make ice-cream. But if salt (NaCl) is present, the temperature of ice from -10°C will increase to -7°C at which it will become constant for some time till all the ice melts. So, in this way we can create a suitable temperature for freezing ice-cream.

Cell Potential of a electrochemical cell

Electrochemical cells have inheritance advantage of higher efficiency as compared to conventional source of electricity generation. In electro-chemical cell the chemical reaction is split in two separate half reactions known as oxidation half reaction and reduction half reaction.
There are two electrodes known as anode and cathode, at anode oxidation takes place while at cathode reduction takes place. During oxidation, electrons are released at the electrode and makes it negative charge while in reduction electrons are used, therefore cathode is positive charge.
As the two reactions are opposite, the potential of the cell is addition of potential of two electrode:
Ecell = E_anode (oxidation potential) + E_cathode (reduction potential)
as oxidation potential = -reduction potential
 Ecell = -E_anode (reduction potential) + E_cathode (reduction potential)
               E_cathode (reduction potential) - E_anode (reduction potential)