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Chemistry Formula for Atomic Structure Part 2

Chemistry Formulas for Atomic Structure

Chemistry Formulas from Bohr’s Model of Atom

·         Angular momentum of electron in nth orbit


Where, m = Mass of the electron,
            v = velocity of electron,
            r = radius of the orbit,
            h = Planck’s constant,
            n = no. of orbit in which electron is present,

·         Energy of electron in nth orbit

            
           Where, Z = Atomic No. of Electron,

·         Energy absorbed or released in an electron jump ( E)

 

·         Radius of orbits of hydrogen like species

              
         For hydrogen atom Z = 1, for first orbit n = 1,
         On substituting values of the constants
         h = 6.62x10-27erg sec,
         m = 9.1x10-28g,
         e = 4.8x10-10
     we get,
    r = 0.529 Å
So, radius of first orbit of hydrogen atom is 0.529 Å.

·         Radius of nth orbits of hydrogen like species

rn = 0.529n2/Z Å

·         Velocity of electron in nth orbit

          
      On substituting values of the constants
      We get,

·         No. of revolution per second made by an electron around the nucleus of atom

·         Energy of electron in nth orbit (En)

       
        On substituting values of the constants
        We get,          
            
         In general,
                          

·         Energy of electron in a Hydrogen Atom in different energy levels

Energy Level
E (Joules/atom)
E (eV/atom)
E (kcal/mol)
1
-21.79x10-19
-13.6
-313.5
2
-5.42x10-19
-3.4
-78.4
3
-2.41x10-19
-1.51
-38.84
4
-1.36x10-19
-0.85
-19.6
5
-0.87x10-19
-0.544
-12.5
Infinite
0
0
0

·         Frequency or wave length of emitted radiation

          
            Where, λ = wavelength of emitted radiations
                        R = Rydberg constant for Hydrogen atom

·         Number of spectral lines produced when an electron drops from nth level to ground level

          

Chemistry Formulas from Photoelectric Effect

·         Planck’s Relationship,

E = hv

·         Total energy,

Total Energy = (mv2/2) + w
Where, w = energy required to remove the electron.

Chemistry Formulas from Wave Mechanical Concept of Atom

·         De Broglie’s Equation,

            
          Where, m = mass of particle,
                        v = velocity of the particle,
                        h = Planck’s Constant,
or,       
          

Chemistry Formulas from Heisenberg’s Uncertainty Principle

·        Heisenberg’s Uncertainty Principle,

            
           Where,   = uncertainty in the position of the particle,
                        = uncertainty in the momentum of the particle,
Also,
           
 

Chemistry Formulas from Quantum Numbers

·         Principle Quantum Number (n),

Maximum no. of electrons in n principle quantum number = 2n2

·         Azimuthal Quantum Number (l),

For the given value of principle quantum number (n), azimuthal quantum number (l), may have all integral values from 0 to (n-1)

·         Magnetic Quantum Number (m),

No. of orbitals in a sub-shell = 2 l +1

·         Spin Quantum Number (s),

For spinning of electron about its own axis

Carbonate Chemical Formula

Carbonate Chemical Formula and Description

Carbonate

It is a salt of the Carbonic Acid characterized by the presence of carbonate ion. Carbonate is a poly-atomic ion with the formula of CO2−
3


Chemical Formula of Carbonate

Carbonate CO2−
3


Structural Formula of Carbonate

Structural Formula of Carbonate

Chemical Properties of Carbonate

Metal carbonates decomposes on heating.

Example of S-Block Carbonates

H2CO3, Li2CO3, Na2CO3

Example of P-Block Carbonates

Al2(CO3)3 , NH4HCO3 , PbCO3

Example of D-Block Carbonates

MnCO3, FeCO3, Ag2CO3 

Humidity

What is Humidity?

The simple meaning of humidity is ‘atmospheric moisture’ or ‘amount of water vapor in the atmosphere’.
what is humidity
 Humidity is the amount of water vapors present in the atmosphere (or air). Water vapors are the gaseous state of water and are invisible.
 Humidity can be measured by three ways that are: absolute, relative and specific.
    1.   Absolute humidity is the water content of air in the gram per cubic meter at a given temperature.
     2.   Relative humidity is expressed in percentage, and it measures the current absolute humidity relative to the maximum humidity for that temperature.
    3.   Specific humidity is expressed as the ratio of the mass of the water vapors to the total mass of moist air parcel.

What is Absolute Humidity?

To understand absolute humidity let’s assume you are standing in ground and you collect some air. Now you check that air volume in your chemistry lab and get accurate amount of water vapors in gram. If you collect 1 cubic meter of air volume and it contains 30 gram water vapors than absolute humidity of that ground air is 30 grams per cubic meter. So, now you answer this question i.e. what is absolute humidity.
Absolute humidity (AH) is defined as the total mass (in gram) of water vapor present in a given volume (in cubic meter) of air. Absolute Humidity changes with changes in air temperature and pressure. Absolute humidity is the mass of the water vapors( m H 2 O ) {\displaystyle (m_{H_{2}O})} divided by the volume of the air and water vapor mixture.
AH = m/V
Where, AH = Absolute humidity,
             m = mass of the water vapors( m H 2 O ) {\displaystyle (m_{H_{2}O})},
             V = volume of the air and water vapor mixture.


What is Relative Humidity?

To understand relative humidity let’s assume you are in a building where air absolute humidity is 15 grams per cubic meter at 25 degree Celsius temperature and at 25 degree Celsius temperature highest amount of water vapors is 30 grams per cubic meter (saturated air with water vapors 15 grams per cubic meter). So, now you can calculate relative humidity as follows:
Relative humidity = (15 grams per cubic meter / 30 grams per cubic meter)x100
                            RH = 50%
So, now you answer this question i.e. what is relative humidity.
Relative humidity (RH) is defined as the ratio of the partial pressure of water vapors to the equilibrium vapor pressure of water at a given temperature. If temperature of the atmosphere is lower than relative humidity is higher as cold air (air with low temperature) holds more water vapors (moisture) but, If temperature of the atmosphere is higher than relative humidity is lower as hot air (air with high temperature) holds less water vapors (moisture).

What is Specific Humidity?

To understand specific humidity let’s assume you have an air parcel (air volume or some amount of air) and this parcel contains 10 gram mass of water vapors and total mass of air is 1 kg (including mass of all gases present in air and mass of water vapors) than specific humidity is 10 gram per kilogram. So, now you answer this question i.e. what is specific humidity.
Specific Humidity is defined as the ratio of the mass of water vapors in air to the total mass of the mixture of air and water vapors.
Specific Humidity = mass of water vapor/total mass of air

Difference between Humidity and Relative Humidity

Before going to discuss about “Difference between Humidity and Relative Humidity” we need to understand that what is humidity and what is relative humidity. And to get answer of these two questions just read above paragraph once again if you don’t understand.
Humidity is the amount of water vapors present in the atmosphere (or air). Relative humidity is expressed in percentage, and it measures the current absolute humidity relative to the maximum humidity for that temperature.


Analytical Balance

Analytical Balance

What is an analytical balance?

what is Analytical Balance
Analytical balance is a lab-instrument used to determine mass of any matter very precisely. These analytical balances are very sensitive and expensive lab-instruments, and also upon the accuracy and precision of analytical balance the accuracy of lab-analysis result depends so handle these balances very carefully. Generally used analytical balances are balances with the capacity of 100 gram to 200 gram and the sensitivity of 0.1 milligram to 0.001 milligram. For any quantitative chemical analysis there is need of analytical balance for the weighing of sample for analysis and weighing of reagents for solution preparation. Analytical balance pan used to put sample on it is enclosed in a glass-fitted case, means analytical balance sensitivity requires that it to be protected by the draft shield or enclosure.
analytical balances

Definition of Analytical Balance

Analytical balance is a lab instrument with a scale to measure the mass to a high degree of precision. Generally used analytical balances are balances with the capacity of 100 gram to 200 gram and the sensitivity of 0.1 milligram to 0.001 milligram.

Where are analytical balances used?

Analytical balances are used in labs so also known as ‘Lab Balances’. In labs analytical balances are used for quantitative analysis like for measuring of sample, preparation of standard solutions etc.

How to weigh on an analytical balance?

These are the following steps to start weighing operation on an analytical balance-
  • Wear hand gloves.
  • Open the door of balance and place the container on pan of analytical balance.
  • Now, close the door of the analytical balance and wait for some time.
  • After some time value on balance display or scale get stabilizes, and shows some weight.
  • Now, press the tare button to get 0.0000 gram reading on display.
  • Add the sample until the required weight.
  • Now, close the door and wait for some time.
  • After some time value on balance display or scale get stabilizes, and shows some weight.
  • Record the net weight.
  • Clean the balance after use.

What is analytical balance uncertainty?

Analytical balance uncertainty is the margin of error in weighing, means when making measurements or weighing there is always an element of uncertainty in measurements or weighing. Determination of measurement uncertainty in analytical balance results is an integral part of the balance calibration.

Why should I calibrate my analytical balance?

Calibration of analytical balance is very necessary because balance calibration ensures that weighing balance is precise, correct, truthful, accurate, and satisfies different standards like ISO, GLP, and GMP. Calibration of analytical balances should be documented, as it specifies the quality of measurements. Documented calibration should be performed repeatedly, at some time intervals (like 3months+/-15days). 

How should I calibrate my analytical balance?

You should not calibrate your balance on your own, but it should be calibrated by third party. Means, calibration of balance is performed by third party authorized service technician.  This third party authorized service technician follow a standard procedure, and utilizes some calibration software to calibrate your analytical balance.

What is the analytical balance minimum weight?

Generally minimum weight of analytical balance is not fixed, means it is different for different balances and it depends on different factors like performance of load cell, location of balance, and surrounding environment. Minimum weight is smallest weight that can be measured with accuracy. If we try to measure below this minimum weight, we get results higher relative measurement uncertainty than the required weighing accuracy. So measurements below minimum weight cannot be trusted.
If you want to determine the minimum weight of your balance, you need to assess measurement uncertainty in the working environment.

Analytical balance accuracy and precision – what is the difference and how to test them?

Precision in balances refers to the closeness of two or more measurements to each other, means if we measure 5gram sample and its display shows 5.0001 in 1st time measurement, 5.0000 in 2nd time measurement, 4.9999 in 3rd measurement, and 5.0000 in 4th measurements so all these results (5.0001, 5.0000, 4.9999, and 5.0000) are very close to each other.
Accuracy in balances means how accurate result it gives so, Accuracy in balances refers to the closeness of a measured value to a known value, and Accuracy in balances is based on repeatability, readability, eccentricity and non-linearity. Accuracy of analytical balance can be tested using
  • A traceable calibrated weight also known as external reference weight having a known mass. And these weights are calibrated by third party and come with documented proof.
  • Accuracy of balance must be determined at its location of use.


Do you know ?

What is Analytical Chemistry ?

Analytical chemistry is all about, what an analytical chemist do in an analytical chemistry lab. And simply we can say that analytical chemistry is the branch of chemistry for qualitative analysis and quantitative analysis of compounds and mixtures by using different test methods and techniques like flame tests, chemical tests, precipitation, titration, chromatography, spectroscopy, separation, microscopy etc.
Definition of Analytical Chemistry- Analytical Chemistry is the branch of chemistry deals with the study of material examination to separate out them into different components and identifying all components and how much these components present in material. There are different analytical methods and techniques to perform these tasks... read more
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