Answer:
D. Intramolecular covalent bond
Explanation:
Compound D is structurally more rigid as a result of intramolecular covalent bonding. The forces that hold together atoms within a compound are greater as compared to forces holding two molecules together (intermolecular bonding). On the other hand Hydrogen bonds are weaker as compared to covalent bonds. Covalent bonds involve the sharing of electrons between two atoms and Hydrogen bonds are formed between a highly electronegative atom like oxygen, Flourine,Chlorine to hydrogen.
The weighted average of the nail in accordance with the given data is 11.176g.
<h3>How to calculate weighted average?</h3>
Weighted average is an arithmetic mean of values biased according to agreed weightings.
The weighted average of the nail in the image above can be calculated by multiplying the decimal abundance with the mass of the nail, then summed up as follows;
Weighted average = (decimal abundance × mass 1) + (decimal abundance × mass 2)
Weighted average = (0.12 × 3.3) + (0.88 × 12.25)
Weighted average = 0.396 + 10.78
Weighted average = 11.176g
Therefore, 11.176g is the weighted average of the nail
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The number of moles of 210 grams of NaHCO₃ is 2.5 moles.
<h3>How to find the Number of moles ? </h3>
To calculate the number of moles use the formula
Number of moles = 
Mass of NaHCO₃ = 210 g
Now we have to find the Molar mass of NaHCO₃
= Atomic mass of Na + Atomic mass of H + Atomic mass of C + 3 (Atomic mass of O)
= 23 + 1 + 12 + 3 (16)
= 36 + 48
= 84 g/mol
Now put the value in above formula we get
Number of moles =
= 
= 2.5 moles
Thus from the above conclusion we can say that The number of moles of 210 grams of NaHCO₃ is 2.5 moles.
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It could not hold good for elements heaver than calcium.
