When a substance is entering a phase change, the gain or loss of heat is a result of:______.
1 answer:
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Answer:
Dipole-dipole attractions
Explanation:
The Cl atom is more electronegative than H, so it attracts the electrons in the H-Cl bond more to itself.
The Cl end of the molecule becomes partially negative (δ-), and the H end becomes more positive (δ+). This separation of charge is called an electric dipole,
When two HCl molecules are near each other, they arrange themselves so that the negative and positive ends of the dipoles line up and attract the two molecules together.
The half-life of cobalt-60 is 5.26 years. After 10.52 years, 5 grams of a 20-gram sample will remain is TRUE
<u>Explanation:</u>
Mass of cobalt = 20 g
Half-life = 5.26 years
Mass remains after 10.52 years = 5 g
This can be solved by using given below formula,
= initial mass
t = number of years from when the mass was m_0
m(t) = remaining mass after t years
Number of half-lives =
Number of half-lives =
Number of half-lives = 2
At time zero = 20 g
At first half-life = = 10 g
At second half life = = 5 g
The given statement is true.
Answer:
Explanation:
Given that:
Concentration of = 0.105 M
Volume of = 20.0 mL
Concentration of = 0.125 M
The chemical reaction can be expressed as:
Using the ICE Table to determine the equilibrium concentrations.
I 0.105 0 0
C -x +x +x
E 0.105 - x x x
Recall that the ka for
Then;
By solving the above mathematical expression;
x = 0.00137 M
pH = 2.86
Hence, the initial pH = 2.86
b) To determine the volume of the added base needed to reach the equivalence point by using the formula:
Thus, the volume of the added base needed to reach the equivalence point = 16.8 mL
c) when pH of 5.0 mL of the base is added.
The Initial moles of molarity × volume
number of moles of 5.0 NaOH = molarity × volume
number of moles of 5.0 NaOH =
After reacting with 5.0 mL NaOH, the number of moles is as follows:
Initial moles
0 0
F(moles) 0
The pH of the solution is then calculated as follows:
Recall that:
pKa for
Then; we replace the concentration with the number of moles since the volume of acid and base are equal
∴
pH = 4.37
Thus, the pH of the solution after the addition of 5.0 mL of NaOH = 4.37
d)
We need to understand that the pH at 1/2 of the equivalence point is equal to the concentration of the base and the acid.
Therefore;
pH = pKa = 4.74
e) pH at the equivalence point.
Here, the pH of the solution is the result of the reaction in the with
The total volume(V) of the solution = V(acid) + V(of the base added to reach equivalence point)
The total volume(V) of the solution = 20.0 mL + 16.8 mL
The total volume(V) of the solution = 36.8 mL
Concentration of = moles/volume
=
= 0.0571 M
Now, using the ICE table to determine the concentration of ;
I 0.0571 0 0
C -x +x +x
E 0.0571 - x x x
Recall that the Ka for =
Hence, the pH of the solution at equivalence point = 8.75
f) The pH after 5.09 mL base is added beyond (E) point.
Before 0.0021 0.002725 0
After 0 0.000625 0.0021
From above; we can determine the concentration of by using the following method:
pH = 12.17
Finally, the pH of the solution after adding 5.0 mL of NaOH beyond (E) point = 12.17