The answer to this question is 2 and 3
Answer: The average atomic mass of oxygen is 15.999 amu
Explanation:
Mass of isotope O-16 = 15.995 amu
% abundance of isotope O-16= 99.759 % = 
Mass of isotope O-17 = 16.995 amu
% abundance of isotope O-17 = 0.037% = 
Mass of isotope O-18 = 17.999 amu
% abundance of isotope O-18 = 0.204% = 
Formula used for average atomic mass of an element :
![A=\sum[(15.995\times 0.99759)+(16.995\times 0.00037)+(17.999 \times 0.00204)]](https://tex.z-dn.net/?f=A%3D%5Csum%5B%2815.995%5Ctimes%200.99759%29%2B%2816.995%5Ctimes%200.00037%29%2B%2817.999%20%5Ctimes%200.00204%29%5D)
Thus the average atomic mass of oxygen is 15.999 amu
We need to know how many valence electrons are present in a given molecule in order to determine its Lewis dot structure.
<h3>
What is Lewis dot structure?</h3>
Lewis dot structure is defined as the visual representation of atoms' electrons using a diagram. It describe the bonds that exist between a molecule's lone pairs of electrons and its atoms.
A lone pair of electrons on the atom with the formal charge of 1- can typically be converted into a bonding pair that is shared with the atom that has the formal charge of 1+ in order to reduce the formal charges when they are present.
Thus, we need to know how many valence electrons are present in a given molecule in order to determine its Lewis dot structure.
To learn more about Lewis dot structure, refer to the link below:
brainly.com/question/20300458
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Ni(OH)2+H2SO4=NiSO4+2H2O
Double Replacement Reaction
