Answer : The correct option is, (A) -x kJ/mol
Explanation :
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 given chemical reaction is,
Now we have to determine the value of 
for the following reaction i.e,
According to the Hess’s law, if we reverse the reaction then the sign of change.
So, the value 
for the reaction will be:
Hence, the value of for the reaction is -x kJ/mole.
Chemical changes are permanent and alter the identity of a sustance
Answer:
mountain
Explanation:
when plates move towards each other they create mountains
Answer:
74.9%.
Explanation:
Relative atomic mass data from a modern periodic table:
- Ca: 40.078;
- C: 12.011;
- O: 15.999.
What's the <em>theoretical</em> yield of this reaction?
In other words, what's the mass of the CO₂ that should come out of heating 40.1 grams of CaCO₃?
Molar mass of CaCO₃:
.
Number of moles of CaCO₃ available:
.
Look at the chemical equation. The coefficient in front of both CaCO₃ and CO₂ is one. Decomposing every mole of CaCO₃ should produce one mole of CO₂.
.
Molar mass of CO₂:
.
Mass of the 0.400655 moles of 
expected for the 40.1 grams of CaCO₃:
.
What's the <em>percentage</em> yield of this reaction?
.
The way to know this is by using the next procedure:
<span>n = c x v
0.665 = 1.15 x v
v = 0.578L = 578mL QED
This is going to help you indeed. Hope its good for you
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