Answer:
The chemical elements are arranged in order of increasing atomic number.
Explanation:
Hydrogen = 1
Helium = 2
Lithium = 3
Answer:

Explanation:
Given,
The density of Helium is 
We need to find the density in Dg/μm
We know that,
1 g = 10 dg
1 cm³ = 10¹² μm³
So,

So, the density of Helium is equal to
.
Answer:
Is called a diluted solution
Explanation:
Having little solute makes the dissolving process in a large amount of solvent very easy to mix therefore it dilutes in the solvent
Answer : The volume of 4.9 M
stock solution used to prepare the solution is, 12.24 ml
Solution : Given,
Molarity of aqueous
solution = 1.20 M = 1.20 mole/L
Volume of aqueous
solution = 50.0 ml = 0.05 L
(1 L = 1000 ml)
Molarity of
stock solution = 4.9 M = 4.9 mole/L
Formula used :

where,
= Molarity of aqueous
solution
= Molarity of
stock solution
= Volume of aqueous
solution
= Volume of
stock solution
Now put all the given values in this formula, we get the volume of
stock solution.

By rearranging the term, we get

Therefore, the volume of 4.9 M
stock solution used to prepare the solution is, 12.24 ml