Oxygen had 6 valence electrons
0.000001ppm
Explanation:
Mass of fluoride = 500g
Volume of water = 500000liters
Unknown:
Parts per million of fluoride = ?
Solution:
The parts per million is the amount of solute in milligram dissolved in a liter of water or milligram per kilogram of solvent
It is a unit used to express very small concentration.
we need to convert g - mg
500g = 500 x 10⁻³mg = 0.5mg
Concentration in parts per million = 
Concentration in parts per million = 
= 0.000001ppm
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Because the reactants react with each other and chemically react to produce a different product like with fire when it reacts with the wood it burns and the product left behind is a new different substance from the reactants in this case the product is ash
The heat will flow from Cu to Fe because Cu has higher temperature and has lower peak value .
Given ,
two aircraft rivets , one iron and the other copper , are placed in a calorimeter .
the initial temp of the calorimeter is 20 degC .
mass of iron = 30 g
initial temp of iron = 0 degC
Mass of copper = 20 g
initial temp of copper = 100 degC
Here copper has higher temp ,thus heat flow from Cu to Fe .
<h3>
What is heat flow ?</h3>
Heat flow is the movement of heat from higher temperature to lower temperature .
<h3>What is calorimeter ?</h3>
It is an object used for measuring the heat flow , heat capacity of a chemical reaction as well as the physical changes .
Learn more about calorimeter here :
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What I think is the charge of nucleus is the proton+neutron
