RELATIVE ATOMIC MASS QUESTIONS

Question 1:
Calculate the relative atomic mass of silver if it occurs naturally as 51.84% silver-107 and 48.18% silver-109.

Solution:
Relative atomic mass = 0.5184 (107) + 0.4816 (109)
Relative atomic mass = 107.96

Question 2:
Calculate the relative abundance of each isotope of copper if it consists of two isotopes, copper-63 and copper-65. Its relative atomic mass is 63.62.

Solution:
Let Abundance of copper-63 = x
Then, Abundance of copper-65 = 1-x

Relative atomic mass = 63x + 65(1-x)
                                      63x + 65(1-x) = 63.62
                                       x = 0.69
That is, 69% of copper-63 and 31% of copper-65

THE MASS SPECTROMETER

The mass spectrometer is an instrument used for analyzing samples of elements and compounds. It consists of six basic stages: Injection, Vaporization,  Ionization, Acceleration, Deflection, and  Detection.

Click to view a diagram of the mass spectrometer.

• The sample is injected into the instrument.
•  It may be vaporized by heating. 
• The vaporized sample is then passed into an ionizing beam of electrons which knock electrons off the sample to create positive ions.
• These positive ions are then accelerated by some electrostatically charged plates into a magnetic field.
• The magnetic field then deflects the particles according to their mass/charge ratio.
• The deflected ions then arrive at the detector.

You can test yourself on the atomiser by clicking this link. It is a timed quiz.

REDOX REACTIONS=OXIDATION + REDUCTION

There are many definitions of oxidation.
1. It is the addition of oxygen to a substance.
2. It is the removal of hydrogen from a substance.
3. It is also the increase in the oxidation state of an element or molecule.
4. It can also be defined as the loss of electrons.

Examples of oxidation:

•  Oxygen-based cleaners use oxidation process for their actions.
• The sterilizing powers of hydrogen peroxide is based on oxidation. 
•  A rusty car is due to oxidation.
•  Browned fruit has oxidation to blame. 

There are many definitions of reduction.
1. It is the removal of oxygen from a substance.
2. It is the  addition of hydrogen to a substance.
3. It is also the decrease in the oxidation state of an element or molecule.
4. It can also be defined as the gain of electrons.

Most of the time, oxidation occurs in tandem with reduction. This is called redox reaction. It comes from oxidation-reduction.  One atom or compound steals electrons from another atom or compound.

Rusting is a classic example of a redox reaction. When rusting happens, oxygen steals electrons from iron. Oxygen is reduced while iron gets oxidized. The resulting compound is called iron oxide, or rust. 

VARIOUS BIOLOGY TOPICS

If you are interested in learning more about various topics in biology. Click to check this website. The information here is more detailed than what you may need to know for the pre-nursing entrance exam but it is worth knowing some of them.

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PROPERTIES OF MATTER

Matter is anything that occupies space and has mass. There are three states of matter:

•  solid
•  liquid
• gas. 

Matter can be classified according to two properties:

•  physical (properties observed without changing the composition of the substance)
•  chemical (properties that describe the tendency of a substance to undergo chemical reactions that change its chemical composition)

Physical properties can be described as:

• intensive or 
• extensive. 

What is an intensive property?

Intensive properties are the same for all samples and do not depend on sample size. Examples: color, physical state, melting and boiling points, optical density. 

What is an extensive property?

Extensive properties depend on the amount of material. and include mass and volume. 

The ratio of two extensive properties, mass and volume, is an important intensive property called density.

What is a physical change?
A physical change involves the conversion of a substance from one state of matter to another, without changing its chemical composition. 

Most matter consists of mixtures of pure substances, which can be:

•  homogeneous (uniform in composition) or 
• heterogeneous (different regions possess different compositions and properties). 

What is a pure substance?
Pure substances can be either chemical compounds or elements. 

What is the difference between a compound and an element?
Compounds can be broken down into elements by chemical reactions, but elements cannot be separated into simpler substances by chemical means.   

Read more by clicking on this link.

LIVEN YOUR DAY WITH THIS JOKE!

One year, James decided to buy his mother-in-law a cemetery plot as a Christmas gift. The following year,  he didn't buy her a gift. When she asked him why, he replied, "Well, you still haven't used the gift I bought you last year!" 

Then a fight broke out.