Answer is (4).<span>
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<span><em>Explanation:</em>
</span><span>
<span>The given mixture contains an </span>insoluble solid<span> <span>and an </span></span>aqueous solution of salt. <span>The insoluble solid is </span>sand. <span>
First </span><span>we have to separate </span>insoluble solid. <span>Sand can be separated by doing </span>filtration. When we filter the mixture sand can be seen as the residue on the filter paper.
<span>After filtering the mixture, we should collect the </span>filtrate. <span>Filtrate is the </span>salt solution. <span>By doing </span>evaporation <span>we can get the </span>solid salt. <span>
First </span>and second choices are wrong <span>because </span>after evaporating water filtration
cannot be done and salt and sand will be mixed together.<span>
Salt cannot be
filtered out because the salt is soluble and it is <span>in
aqueous medium. Hence, third choice is wrong</span></span></span>
# of atoms per mol = Avogadro’s # (6.022 x 10^23)
Number of mols = mass of substance / molar mass
73 g / 40.08 g = 1.8 mols of Ca in 73 grams
1.8 mols x avagadro’s # = 1.1 x 10^24 atoms in 73 grams of Ca
PH stands for "Potential Hydrogen" and the PH scale ranges from 0-14. PH refers to the ability to attract hydrogen ions.
The PH of a solution either indicates acidity of the solution or alkalinity of the solution. A solution which has PH 7 above is a base solution where a solution with PH less than 7 is an acidic solution.
Answer : The Lewis-dot structure of 
is shown below.
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 hydrogen has '1' valence electron and nitrogen has '5' valence electrons.
Therefore, the total number of valence electrons in = 5 + 3(1) = 8
According to Lewis-dot structure, there are 6 number of bonding electrons and 2 number of non-bonding electrons.
Now we have to determine the formal charge for each atom.
Formula for formal charge :
Hence, the Lewis-dot structure of is shown below.
