A is obviously out because it leads to a volume of 125.0 milliliters of the new solution and gives you a lower concentration than you were aiming for.
D is out because you are adding 75 milliliters of the stock solution, so your concentration would be too high. You only need 25.0 milometers of stock solution per 100 milliliters of the new solution.
C is also out because it leads to 50.0 milliliters stock solution per 100 milliliters of the new solution and hence the wrong concentration.
B is by default the correct answer. It also details the correct technique. First you add the stock solution (This you know from your calculations to be 25 milliliters.) then you add the water up to the volume you needed. (Because the calculations only tell you the total volume of water not what you need to add) You also add the water last so you can rinse the neck of the flask to make sure you also get all the stock solution residue into the stock solution.
I would add the final step of stirring, but B is the only answer that can be correct.
Answer:
c. rate=−1/2Δ[HBr]/Δt=Δ[H2]/Δt=Δ[Br2]/Δt
Explanation:
Hello,
In this case, the undergoing chemical reaction is:
Thus, the rate is given as:
![rate=-\frac{1}{2} \frac{\Delta [HBr]}{\Delta t}=\frac{\Delta [Br_2]}{\Delta t} =\frac{\Delta [H_2]}{\Delta t}](https://tex.z-dn.net/?f=rate%3D-%5Cfrac%7B1%7D%7B2%7D%20%5Cfrac%7B%5CDelta%20%5BHBr%5D%7D%7B%5CDelta%20t%7D%3D%5Cfrac%7B%5CDelta%20%5BBr_2%5D%7D%7B%5CDelta%20t%7D%20%3D%5Cfrac%7B%5CDelta%20%5BH_2%5D%7D%7B%5CDelta%20t%7D)
It is necessary to remember that each concentration to time interval is divided into the stoichiometric coefficient, that is why HBr has a 1/2. Moreover, the concentration HBr is negative since it is a reactant and it has a negative rate due to its consumption.
Therefore, the answer is:
c. rate=−1/2Δ[HBr]/Δt=Δ[H2]/Δt=Δ[Br2]/Δt
Best regards.
Answer:
Option D. pH= 1.3 strong acid
Explanation:
From the question given:
The hydrogen ion concentration [H+] = 0.05 M
pH = —Log [H+]
pH = —Log 0.05
pH = 1.3
Since the pH lies between 0 and 7, the solution is acidic. Since the pH value is low, the solution is a strong acid
A forest fire is considered a chemical change because of the changing of the wood by combustion, which is not a physical change.
Answer:
19.91 J/K
Explanation:
The entropy is a measure of the randomness of the system, and it intends to increase in nature, thus for a spontaneous reaction ΔS > 0.
The entropy variation can be found by:
ΔS = ∑n*S° products - ∑n*S° reactants
Where n is the coefficient of the substance. The value of S° (standard molar entropy) can be found at a thermodynamic table.
S°, Cl(g) = 165.20 J/mol.K
S°, O3(g) = 238.93 J/mol.K
S°, O2(g) = 205.138 J/mol.K
So:
ΔS = (1*205.138 + 1*218.9) - (1*165.20 + 1*238.93)
ΔS = 19.91 J/K
