Answer:
3,116J/K
Explanation:
This question asks to calculate the entropy change of the surroundings.
To do this, we need the standard enthalpy of formation ΔfH° of the reacting species and products first:
We should observe that standard enthalpy if formation of O2 is zero. We proceed with the rest of the species.
H2CO = -109.5KJ/mol
CO2 = -393.5KJ/mol
H2O = -285.8KJ/mol
Now, we calculate the standard change of enthalpy of the reaction as:
ΔHrxn = ΔHproduct - ΔHreactant = (-285.8 - 393.5) +(109.5) = -569.8 KJ/mol
The relationship between the entropy and the standard formation enthalpy is given as
The relationship is:
ΔSosurroundings = - ( ΔHof/ T)
We convert the standard enthalpy of formation to joules first = -569.8 * 10^3 Joules
Using the formula above at a temperature of 298k, the entropy change would be:
-(-569.8 * 10^3)/298 = 1912J/K
Now, we know that 1.63 moles of H2CO reacted. We also need to know the coefficient of the H2CO in the reaction which is 1.
We thus have:
1.63 mol H2CO(g) * (1912J/K * 1 mol H2CO) = 3116J/K
The best and most correct answer among the choices provided by the question is the fourth choice "<span>Each fluorine atom will take 1 valence electron from the other, and this will constantly happen back and forth." This is because the 7 valence electrons are difficult to remove.</span>
I hope my answer has come to your help. God bless and have a nice day ahead!
Answer:
1. Decrease the pH
2. The pH remains unchanged
3. Decrease the pH
Explanation:
We can calculate the pH of a weak acid using the following expression:
![pH=-log [H^{+} ]=-log\sqrt{Ka \times Ca }](https://tex.z-dn.net/?f=pH%3D-log%20%5BH%5E%7B%2B%7D%20%5D%3D-log%5Csqrt%7BKa%20%5Ctimes%20Ca%20%7D)
[1]
where,
Ka is the acid dissociation constant
Ca is the initial concentration of the acid
<em>State whether each of the following would increase, decrease, or leave the initial pH unchanged and explain your reasoning</em>
- <em>Using the same weak acid, but having a higher concentration. </em>According to eq. [1], a higher Ca leads to a higher [H⁺] and a lower pH.
- <em>Using 80.00 mL of this weak acid instead of 40.00 mL.</em> pH refers to a concentration, which is an intensive property, so it does not change when we change the amount of matter.
- <em>Using a different weak acid that has a larger Ka value.</em> According to eq. [1], a higher Ka leads to a higher [H⁺] and a lower pH.
1 cm ------------ 10 mm
5,678 cm ------- ?
5,678 x 10 / 1 => 56,78 mm
