Answer : The chemical formula of pure substances are different from those of mixtures because all the matter that exists on earth can be classified into two categories namely; pure substances and mixtures.
A pure substance always consists of a single element or compound. Example Oxygen is formed only of oxygen (O) atoms; whereas the table salt which is formed only by sodium chloride (NaCl) molecules is a compound which is made up of pure elements. A pure substance cannot be further divided into its components.
A mixture is made up of different compounds and/or elements. It can be easily separated using any physical method. Example, sand, salt and saw dust mixed together as a mixture. Also, it will not have a definite chemical formula.
Please refer the attachment for better understanding.
Answer:
C. 101.5°C
Explanation:
The computation of the boiling point of a solution is shown below:
As we know that

where,
i = Factor of Van’t Hoff i.e 2KBr
K_b = Boiling point i.e 0.512° C
m = molality 
Now place the values to the above formula
So, the boiling point is

After solving this, the t is
= 100° C + 1.536° C
= 101.536° C
Hence, the correct option is C.
Bed rock is a layer underneath minerals
Answer: 2.223
Explanation:
HClO4, also known as perchloric acid, is a very strong. This means we can assume that complete dissociation occurs.
This means that:
[H+] = [HClO4] = <span>0.00598
pH = -log[H+]
pH = -log[</span><span>0.00598] = 2.223
Note: The base of the log is 10 (conventionally we don't write the base if it is 10)</span>