This is your answer:
-13 degrees C
Answer:
The correct answer is option D
Ali is using a specialized headphone that cancels the extra noise in the atmosphere.
Megan is using a transmitter to convert electrical signals into radio waves.
Kristoff is using a microphone to convert sound waves into the electrical signals.
Jenna is using the radio to convert radio waves into sound waves.
<u>Answer:</u> The enthalpy of the formation of
is coming out to be -65.3 kJ/mol
<u>Explanation:</u>
Enthalpy change is defined as the difference in enthalpies of all the product and the reactants each multiplied with their respective number of moles. It is represented as 
The equation used to calculate enthalpy change is of a reaction is:
![\Delta H^o_{rxn}=\sum [n\times \Delta H^o_f_{(product)}]-\sum [n\times \Delta H^o_f_{(reactant)}]](https://tex.z-dn.net/?f=%5CDelta%20H%5Eo_%7Brxn%7D%3D%5Csum%20%5Bn%5Ctimes%20%5CDelta%20H%5Eo_f_%7B%28product%29%7D%5D-%5Csum%20%5Bn%5Ctimes%20%5CDelta%20H%5Eo_f_%7B%28reactant%29%7D%5D)
For the given chemical reaction:

The equation for the enthalpy change of the above reaction is:
![\Delta H^o_{rxn}=[(1\times \Delta H^o_f_{(SiC(s))})+(2\times \Delta H^o_f_{(CO(g))})]-[(1\times \Delta H^o_f_{(SiO_2(s))})+(3\times \Delta H^o_f_{(C(s))})]](https://tex.z-dn.net/?f=%5CDelta%20H%5Eo_%7Brxn%7D%3D%5B%281%5Ctimes%20%5CDelta%20H%5Eo_f_%7B%28SiC%28s%29%29%7D%29%2B%282%5Ctimes%20%5CDelta%20H%5Eo_f_%7B%28CO%28g%29%29%7D%29%5D-%5B%281%5Ctimes%20%5CDelta%20H%5Eo_f_%7B%28SiO_2%28s%29%29%7D%29%2B%283%5Ctimes%20%5CDelta%20H%5Eo_f_%7B%28C%28s%29%29%7D%29%5D)
We are given:

Putting values in above equation, we get:
![624.6=[(1\times \Delta H^o_f_{(SiC(s))})+(2\times (-110.5))]-[(1\times (-910.9))+(3\times (0))]\\\\\Delta H^o_f_{(SiC(s))}=-65.3kJ/mol](https://tex.z-dn.net/?f=624.6%3D%5B%281%5Ctimes%20%5CDelta%20H%5Eo_f_%7B%28SiC%28s%29%29%7D%29%2B%282%5Ctimes%20%28-110.5%29%29%5D-%5B%281%5Ctimes%20%28-910.9%29%29%2B%283%5Ctimes%20%280%29%29%5D%5C%5C%5C%5C%5CDelta%20H%5Eo_f_%7B%28SiC%28s%29%29%7D%3D-65.3kJ%2Fmol)
Hence, the enthalpy of the formation of
is coming out to be -65.3 kJ/mol.
<h3><u>Answer;</u></h3>
pH = 4.20
<h3><u>Explanation;</u></h3>
pKa = -log(6.30 × 10^-5)
pKa = 4.20
Moles of Benzoic acid = volume × molarity
= 0.050L × 1.00M
= 0.050moles benzoic acid
Moles of the salt = 0.050L × 1.00M
= 0.050 moles salt
Therefore;
0.050mols / 0.1 L = 0.50M
0.050mols / 0.1 L = 0.50M
Thus;
pH = 4.20 + log(0.50/0.50)
pH = 4.20