A typical deposit of cholesterol,C27H460,in an artery has a mass of 3.90mg.how many molecules of cholesterol are present in this
1 answer:
Answer:
6.074 X 10¹⁸ molecules.
Explanation:
Molecular mass(MM) of this compound C₂₇H₄₆O
= 27*(MM of C) + 46*(MM of H) + (MM of O)
= 27*(12.0107) + 46* (1.00784) + (15.999)
= 324.2889 + 46.36064 + 15.999
=386.64854 g
The mass of a mole of any compound is called it's molar mass. 1 molar mass has 6.022 X 10²³, or Avogadro's number, C₂₇H₄₆O molecules.
If 386.64854 g of C₂₇H₄₆O has 6.022 X 10²³ molecules of cholesterol, then
3.9mg or 0.0039g of C₂₇H₄₆O will have how many molecules?..
Using unitary method:
Number of molecules =
= 6.074 X 10¹⁸ molecules.
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HA ⇄ H⁺ + A⁻
so:
![\frac{[H^+][A^-]}{[HA]} = 1.5 x 10^{-5}](https://tex.z-dn.net/?f=%20%5Cfrac%7B%5BH%5E%2B%5D%5BA%5E-%5D%7D%7B%5BHA%5D%7D%20%3D%201.5%20x%2010%5E%7B-5%7D%20%20)
and now:
= 1.5 x 10⁻⁵
x is considered very small compared to 0.15
x² = 2.25 x 10⁻⁶
x = 1.5 x 10⁻³
So [H⁺] = 1.5 x 10⁻³
pH = - log [H⁺] = - log (1.5 x 10⁻³) = 2.83
so:
and now:
x is considered very small compared to 0.15
x² = 2.25 x 10⁻⁶
x = 1.5 x 10⁻³
So [H⁺] = 1.5 x 10⁻³
pH = - log [H⁺] = - log (1.5 x 10⁻³) = 2.83