50 points pls help me asap!!!!
1. How many grams of 0.5% propanoic acid CH3CH2COOH solution is required to dissolve 6 grams of hydroxyapatite?
2. Calculate mass of SiO2 contained in 2 g of high-fusing porcelain.
3. How many grams of sulphate dihydrate must be heated to get 10 grams of sulphate hemihydrates?
There are 1200 grams of the 0.5% propanoic acid solution is needed to dissolve 6 grams of hydroxyapatite. The mass of SiO2 contained in 2 g of high-fusing porcelain is 1.4 grams. 12.57 grams sulphate dihydrate must be heated to get 10 grams of sulphate hemihydrates.
Mass of propanoic acid in 1 gram of solution = (0.5/100) grams
Mass of propanoic acid in X grams of solution = (0.5/100) × X grams
the propanoic acid solution is 0.5% (0.5/100), it intends there is 0.005 grams of propanoic acid in 1 gram of the solution.
Now relay on the proportion:
(0.005 grams of propanoic acid) / (1 gram of solution) = (6 grams of hydroxyapatite) / (X grams of solution)
Cross-multiplying, we get:
0.005 × X = 6
Solving for X:
X = 6 / 0.005
X = 1200 grams.
Therefore, 1200 grams of the 0.5% propanoic acid solution is needed to dissolve 6 grams of hydroxyapatite.
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A student titrates 25.0 mL of an unknown base with 0.10 M HCl. During the titration the pH is monitored and the collected data is recorded. These data are shown in the table below.
Volume
Added(mL) pH
0.0 11.13
5.0 9.86
10.0 9.44
12.5 9.26
15.0 9.08
20.0 8.66
22.0 8.39
24.0 7.88
25.0 5.28
26.0 2.70
28.0 2.22
30.0 2.00
35.0 1.70
37.5 1.61
40.0 1.52
45.0 1.40
50.0 1.30
a. Use the information provided to draw a titration curve showing the pH as a function of the volume of added HCl. Be certain to label your axes.
b. Identify the equivalence point on your graph and justify your selection of this particular point.
b. Use the data to determine the Kb value for the weak base. Be certain to show the mathematical steps you take to arrive at the answer. Report your final answer to the correct number of significant digits.
c. The student has three indicators that she could use for this experiment. The indicators (with their endpoints) are: Bromophenol Blue (3.0 – 4.6), Methyl Red (4.2 – 6.3), and phenolphthalein (8.3 – 10.0). Which indicator would be appropriate for this titration? Justify your selection.
e. Determine the (i) molarity and the (ii) % ionization of the original weak base solution (before titrating). Report your answers to the correct number of significant digits.
a. Titration Curve:
On the x-axis, label it as "Volume of HCl added (mL)"
On the y-axis, label it as "pH"
b. Equivalence Point:
The equivalence point is the point in the titration where the moles of acid (HCl) added are stoichiometrically equivalent to the moles of base (unknown base) present initially. In the given data, the equivalence point can be estimated to be around 25.0 mL of HCl added. This is where the pH drops dramatically from 7.88 to 5.28, indicating the neutralization of the base.
c. Calculation of Kb Value:
To determine the Kb value, we need to find the pOH at half-neutralization, where half the volume of the equivalent point has been reached. In this case, the half-neutralization volume is 12.5 mL (half of 25 mL).
From the data, we can observe that at 12.5 mL of HCl added, the pH is 9.26.
pOH = 14 - pH = 14 - 9.26 = 4.74
pOH = -log[OH-]
[OH-] = 10^(-pOH)
[OH-] = 10^(-4.74)
To find [OH-] in moles per liter (M), we need to convert mL to L.
[OH-] = 10^(-4.74) mol/L
Now, since we know that at the equivalence point, the concentration of the acid (HCl) is 0.10 M, we can use the stoichiometry of the reaction to determine the concentration of the base (unknown base).
From the balanced equation:
HCl + OH- → H2O + Cl-
1 mole of HCl reacts with 1 mole of OH-
0.10 M (HCl) = [OH-] M (unknown base)
Therefore, Kb = [OH-][unknown base] / [base]
Kb = (10^(-4.74) mol/L)(0.10 M) / (0.10 M - 10^(-4.74) M)
Simplify and calculate Kb.
c. Selection of Indicator:
Based on the given pKa ranges of the indicators, the indicator phenolphthalein (pKa range: 8.3 - 10.0) would be appropriate for this titration. The reason is that the pH at the equivalence point is expected to be around 7, which is well within the range of phenolphthalein's color change. Bromophenol Blue and Methyl Red have lower pKa values and would not be suitable for indicating the equivalence point in this particular titration.
d. Calculation of Molarity and % Ionization of the Weak Base Solution:
To calculate the molarity of the weak base solution, we can use the Henderson-Hasselbalch equation:
pH = pKa + log([A-]/[HA])
At the half-neutralization point, [A-] = [HA], and the pH is 9.26.
9.26 = pKa + log([A-]/[HA])
The pKa can be determined using the pOH at half-neutralization:
pKa = 14 - pOH = 14 - 4.74 = 9.26
9.26 = 9.26 + log([A-]/[HA])
log([A-]/[HA]) = 0
[A-]/[HA] = 10^0 = 1
Since [A-] = [HA], the concentration of the weak base (before titration) is equal to the concentration of its conjugate acid.
Therefore, the molarity of the weak base solution is 0.10 M.
To calculate the % ionization of the weak base, we can use the formula:
% Ionization = ([A-]/[HA]) × 100
% Ionization = (1/0.10) × 100
% Ionization = 1000%
Note: The % ionization may exceed 100% in cases where the concentration of the conjugate acid is very small compared to the concentration of the weak base.
Derive the Henderson - Hassebalch equation
The Henderson-Hasselbalch equation can be given as
[tex]p^{H}[/tex] = [tex]pK_{a}[/tex] + log [tex]\frac{[A^{-}] }{[HA]}[/tex]
This equation relates the [tex]p^{H}[/tex] , dissociation constant and concentration of acid and its conjugate base or base and its conjugate acid.
The Henderson-Hasselbalch equation can be derived as,
Let us consider the ionization of weak acid,
HA + [tex]H_{2}O[/tex] ⇄ [tex]H^{+}[/tex] + [tex]A^{-}[/tex]
The dissociation constant [tex]K_{a}[/tex] can be given as
[tex]K_{a}[/tex] = [tex]\frac{[H^{+}][A^{-}] }{[HA]}[/tex]
Rearranging the equation,
[tex][H^{+}][/tex] = [tex]K_{a}[/tex] ×[tex]\frac{[HA]}{[A^{-}] }[/tex]
Taking log on both sides,
log[tex][H^{+}][/tex] =log{ [tex]K_{a}[/tex] ×[tex]\frac{[HA]}{[A^{-}] }[/tex])
log [tex][H^{+}][/tex] = log [tex]K_{a}[/tex] +log [tex]\frac{[HA]}{[A^{-}] }[/tex]
multiplying the whole equation on both the sides
-log [tex][H^{+}][/tex] = - log [tex]K_{a}[/tex] - log [tex]\frac{[HA]}{[A^{-}] }[/tex]
we know that -log [tex][H^{+}][/tex] = [tex]p^{H}[/tex] and - log [tex]K_{a}[/tex] =p[tex]K_{a}[/tex]
then, the equation can be rewritten as
[tex]p^{H}[/tex] = p[tex]K_{a}[/tex] - log [tex]\frac{[HA]}{[A^{-}] }[/tex]
[tex]p^{H}[/tex] = p[tex]K_{a}[/tex] + log[tex]\frac{[A^{-}] }{[HA]}[/tex]
[tex][A^-}][/tex] = Concentration of conjugate base
[HA] = Concentration of weak acid,
So the Henderson-Hasselbalch equation can be modified as,
[tex]p^{H}[/tex] = [tex]pK_{a}[/tex] + log([Conjugate base]/ [weak acid])
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if it takes 38.70cm3 of 1.90M NaOH to neutralize 10.30cm3 of H2SO4 in a battery, what is the concentration of the H2SO4?
To determine the concentration of H2SO4, we can use the concept of molarity (M) and the equation:
M1V1 = M2V2
where:
M1 = concentration of NaOH (in this case, 1.90 M)
V1 = volume of NaOH used (in this case, 38.70 cm^3)
M2 = concentration of H2SO4 (what we're trying to find)
V2 = volume of H2SO4 used (in this case, 10.30 cm^3)
Rearranging the equation, we have:
M2 = (M1 * V1) / V2
Substituting the given values:
M2 = (1.90 M * 38.70 cm^3) / 10.30 cm^3
M2 ≈ 7.12 M
Therefore, the concentration of H2SO4 is approximately 7.12 M.
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Can anyone help please.......
Increasing the concentration of CO decreases the equilibrium concentration of oxygen and increases the concentration of CO₂, increasing the concentration of CO₂ increases the concentration of CO and O₂.
Chemical equilibrium refers to the state of a system in which the concentration of the reactant and the concentration of the products do not change with time, and the system does not display any further change in properties.
It is the state of a reversible reaction where the rate of the forward reaction equals the rate of the reverse reaction. While a reaction is in equilibrium the concentration of the reactants and products are constant.
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Find out the pH of the solution using a hydrogen electrode which is coupled with a saturated calomel electrode . The emf of the combined cell is 0.523 at 25 degree celsius
The pH of the solution, determined by the hydrogen electrode coupled with the saturated calomel electrode, is approximately 9.53.
To find the pH of the solution using a hydrogen electrode coupled with a saturated calomel electrode, we can utilize the Nernst equation, which relates the measured cell potential to the concentration of hydrogen ions in the solution. The Nernst equation is given by:
E = E° - (0.0592/n) * log[H+]
Where E is the measured cell potential, E° is the standard cell potential, n is the number of electrons transferred in the half-reaction (which is 2 for the hydrogen electrode), and [H+] is the concentration of hydrogen ions.
In this case, the emf of the combined cell is given as 0.523 V. Since the saturated calomel electrode (SCE) is the reference electrode, we can consider its standard cell potential (E°) to be 0.241 V at 25 degrees Celsius.
0.523 V = 0.241 V - (0.0592/2) * log[H+]
Simplifying the equation:
0.523 V - 0.241 V = -0.0296 * log[H+]
0.282 V = -0.0296 * log[H+]
Dividing both sides by -0.0296:
log[H+] = -0.282 V / -0.0296
log[H+] ≈ 9.53
Taking the antilog (base 10) of both sides:
[H+] ≈ 10^9.53
[H+] ≈ 3.2 × 10^9 M
Therefore, the pH of the solution, determined by the hydrogen electrode coupled with the saturated calomel electrode, is approximately 9.53.
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A sample of sodium trioxocarbonate(IV) containing sand was dissolved in excess tetraoxosulphate (V) acid and filtered to obtain solution A. B is a solution containing 0.096mol of NaOH per dm³ of solution. Solution A was poured into the burette and titrated against 25cm³ portion of B using methyl orange as indicator. The exercise was repeated to obtain consistent titre values. Assuming that the average titre value is 19.60cm³. Calculate i) The concentration of excess tetraoxosulphate (IV) acid in A in mol/dm³ ii) The mass of sand in the sample if 9.00g of the impure sodium trioxocarbonate (IV) reacted with 1dm³ of 0.10M solution of the acid [H=1.0, C=12, O=16.0, Na-23.0, S=32.0]
The concentration of excess tetraoxosulphate (IV) acid in solution A is 0.192 mol/dm³.
How to calculate the valueAverage titre value = 19.60 cm³
Concentration of NaOH in solution B = 0.096 mol/dm³
Volume of solution B = 25 cm³ = 25/1000 dm³ = 0.025 dm³
The balanced equation for the reaction between NaOH and H₂SO₄ is:
2 NaOH + H₂SO₄ → Na₂SO₄ + 2 H₂O
From the equation, we can see that 2 moles of NaOH react with 1 mole of H₂SO₄.
Therefore, the moles of H₂SO₄ in solution B can be calculated as:
Moles of H₂SO₄ = 2 × Moles of NaOH
= 2 × 0.096 mol/dm³
= 0.192 mol/dm³
Since the average titre value is the volume of solution A needed to react with solution B, the moles of H₂SO₄ in solution A is also 0.192 mol/dm³.
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Contrast the theme “farewells are bittersweet” in the excerpts from Melville’s “Redburn: His First Voyage” and Hoffman’s “A Sailor of King George.”
At least 300 words please
The excerpts from Melville’s “Redburn: The idea of having to go made the protagonist so dejected and gloomy that he was on the edge of tears.
In Hoffman's "A Sailor of King George," on the other hand, the theme of "farewells are bittersweet" is seen from the perspective of a seaman who has spent his whole life at sea.
He recalls his extended career and all the farewells he had to give to friends, family, and fellow sailors. It was the end of a long and interesting career, and as I stood on the platform of the old ship and watched the shoreline fade into the distance, I had a strange mix of emotions.
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