Answer:
-1605.1 kJ
Explanation:
The enthalpy of formation is the enthalpy of the reaction that forms the substance only by its constituents, so, substances formed by one element, such as O2, in its ambient temperature phase, have an enthalpy of formation 0.
The enthalpy is a measure of how much heat the system contains, and so, the variation of it measures the heat lost (ΔH <0) or gained (ΔH >0), and for a reaction:
ΔHrxn = ∑ni*ΔHi products - ∑ni*Hi reactants
Where ni represents the coefficient of the substance, so by the data given:
ΔHrxn = [2*(-241.82) + (-393.5)] - [-74.6]
ΔHrxn = -802.54 kJ/ mol of CH4
Thus, the heat released is the enthalpy multiplied by the number of moles of CH4:
Q = -802.54*2
Q = -1605.1 kJ
Not sure but I would say because each orbital around the nucleus of the atom resembles a fuzzy cloud around the nucleus!
The amount of N2O5 to start with would be 35.79 grams
<h3>Stoichiometric calculations</h3>
From the balanced equation of the reactions:
Mole ratio of N2O5 and NO2 = 1:2
Since the reaction's actual yield is 82%, the theoretical yield would be: 25 x 100/82 = 30.49 grams
Mole of 25 g NO2 = 30.49/46
= 0.66 mole
Equivalent mole of N2O5 = 0.54/2 mole
= 0.33 moles
Mass of 0.27 mole N2O5 = 0.33 x 108.01
= 35.79 grams
More on stoichiometric calculations can be found here: brainly.com/question/8062886
<span>Answer: a mixture.
</span><span>Justification:</span>
<span /><span>
</span><span>1) Pure substances have a definite chemical formula: the same kind of atoms with the same fixed ratios and chemical bonds. Therefore, the percents of each element do not varye.
</span>
<span /><span /><span>
2) Elements and compounds are pure substaces. For example, Fe, Mg, Ti, are elements, and CO₂, CO, H₂CO₃ are compounds. Each of them will have always the same kind of atoms, in the same ratio and with the same chemcial bonds. Therefore the percents of the elements do not varye.
</span><span />
<span>3) Mixtures are formed by the physical combination (not chemical bonds) of different elements or compounds in variable proportions. As indicated, this describes the material bronze, in virtue of the variation of its composition. Other examples of mixtures are solutions (like brines), air, ocean water, and milk: different brines, different oceans and different milk have different contents of elements or compounds.
</span><span>
</span>
The answer is option C.
That is it is a heterogeneous mixture.
Heterogeneous mixture have the following properties:
1. Different components could be observed in the substance.
2. Different samples of the substance appeared to have different proportions of the components.
3.The components could be easily separated using filters and sorting.