The objects which cannot be observed in detail without a microscope
include the following:
<h3>What is a Microscope?</h3>
A microscope is an instrument which is used to view smaller objects such as
microbe,cells, tissues etc. This instrument is used in viewing the different
cells found in the body as they can't be seen with the eye.
The remaining options which can be seen with the eyes don't require
the use of microscopes.
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Answer :
The number of bonding pairs of electrons around the hydrogen atom = 2
The number of lone pairs of electrons around the hydrogen atom = 0
Explanation :
Lewis-dot structure : It shows the bonding between the atoms of a molecule and it also shows the unpaired electrons present in the molecule.
In the Lewis-dot structure the valance electrons are shown by 'dot'.
The given molecule is, 
As we know that carbon has '4' valence electrons, hydrogen has '1' valence electrons and nitrogen has '5' valence electrons.
Therefore, the total number of valence electrons in
= 1 + 4 + 5 = 10
According to Lewis-dot structure we conclude that, there are 8 number of bonding electrons and 2 number of non-bonding electrons.
The number of bonding pairs of electrons around the hydrogen atom = 2
The number of lone pairs of electrons around the hydrogen atom = 0
Answer : The formula unit of Sr & Cl is
and the formula unit of Al & S is 
Explanation :
Formula unit : it is defined as the lowest number ratio of ions of an elements in an ionic compound or covalent compound.
For the formula unit of Sr & Cl, two chloride ions
are needed to neutralize the one strontium ion
.
For the formula unit of Al & S, three sulfide ions
are needed to neutralize the two aluminium ion
.
The formula unit of
and
are shown below.
The mass percent lithium hydroxide in the mixture with potassium hydroxide, calculated from the equivalence point in the titration of HCl with the mixture, is 19.0%.
The mass percent of lithium hydroxide can be calculated with the following equation:
(1)
Where:
(2)
We need to find the mass of LiOH.
From the titration, we can find the number of moles of the mixture since the number of moles of the acid is equal to the number of moles of the bases at the equivalence point.



Since mol = m/M, where M: is the molar mass and m is the mass, we have:
(3)
Solving equation (2) for m_{KOH} and entering into equation (3), we can find the mass of LiOH:
Solving for
, we have:

Hence, the percent lithium hydroxide is (eq 1):
Therefore, the mass percent lithium hydroxide in the mixture is 19.0%.
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I hope it helps you!