Answer : The standard enthalpy of formation of methane is, -74.8 kJ/mole
According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.
According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.
The formation reaction of 
will be,
The intermediate balanced chemical reaction will be,
(1) 
(2) 
(3) 
Now we will reverse the reaction 1, multiply reaction 3 by 2 then adding all the equations, we get :
(1) 
(2)
(3) 
The expression for enthalpy of formation of will be,
Therefore, the standard enthalpy of formation of methane is, -74.8 kJ/mole
Answer:
1.30 mol P
Explanation:
take what is given to you (40.4g). now divide it by the molar mass of the asked element (phosphorus = 30.97g/mol)
40.4g P / 30.97g/mol P = 1.30 mol P
hope this helps :)
1. Coefficient
Since it is a number that constant for the given substance
<span>Because it causes more collisions of molecules per second and collisions have higher energy because of higher temperature. </span>
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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
Learn more about weighted average at: brainly.com/question/28042295
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