On the basis of the information above, a buffer with a pH = 9 can best be made by using
A pure NaH2PO4
B H3PO4 + H2PO4–
C H2PO4– + PO42–
D H2PO4– + HPO42–
E HPO42– + PO43
Answer:
D H2PO4– + HPO42–
Explanation:
The acid dissociation constant for [tex]\mathbf{H_3PO_4 , H_2PO^{-}_4 , HPO_4^{2-}}[/tex] are [tex]\mathbf{7\times 10^{-3}, \ \ 8\times 10^{-8} ,\ \ 5\times 10^{-13}}[/tex] respectively.
[tex]\mathbf{pka (H_3PO_4) = -log (7\times 10^{-3} )=2.2}[/tex]
[tex]\mathbf{pka (H_2PO_4^-) = -log (8\times 10^{-8} )=7.1}[/tex]
[tex]\mathbf{pka (HPO_4^{2-}) = -log (5\times 10^{-13} )=12.3}[/tex]
The reason while option D is the best answer is that, the value of pKa for both
[tex]\mathbf{H_2PO^{-}_4 ,\ \& \ HPO_4^{2-}}[/tex] lies on either side of the desired pH of the buffer. This implies that one is slightly over and the other is slightly under.
Using Henderson-Hasselbach equation:
[tex]\mathbf{pH = pKa + log \Big( \dfrac{HPO_4^{2-}}{H_2PO_4^-} \Big)}[/tex]
The compounds that are used for the formulation of the pH 9 buffer are [tex]\rm H_2PO_4^-\;and\;HPO_4^+[/tex]. Thus, option D is correct.
The buffers are the solutions of acids and base of appropriate pH, that are able to limit the change in pH in the reaction mixture.
Which compound is used for pH 9 buffer?The buffer pH is adjusted with the compounds that has been able to add base or acid to the solution.
For the formulation of buffer of specific pH, the acid and base solutions are required.
The compounds that are used for the formulation of the pH 9 buffer are [tex]\rm H_2PO_4^-\;and\;HPO_4^+[/tex], as they are able to provide acid and base to the solution.
Thus, option D is correct.
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The yield for a particular well is 280 gallons per minute (gpm). Of the drawdown for this well is 23 feet, what is the specific yield in gpm/ft?
Answer:
[tex]Y=12.2 \frac{gpm}{ft}[/tex]
Explanation:
Hello!
In this case, since we can find that the well produces 280 gpm, and the given drawdown is 23 ft, we need to divide 280 by 23 to obtain the yield in gmp/ft as shown below:
[tex]Y=\frac{280gpm}{23ft} \\\\Y=12.2 \frac{gpm}{ft}[/tex]
Best regards!
How many moles of MgCl2 can be made from 10 moles of Cl2?
_Mg + _Cl2 -->_MgCl2
(A) 10 moles MgCl2
(B) 11 moles MgCl2
(C) 8 moles MgCl
(D) 15moles MgCl
can someone please help me asap ill mark u brainlest
Answer:It is the ground state of NA
Please help me I need this really quick
Answer:
The answer is (a)
.
.
......................................................................
Describe how moving the mountain lions could affect the ecosystem
Answer:
If Mountain lions are removed from a habitat/ecosystem, their prey will overpopulate, which may lead to extinctions on the pray of the secondary consumers. ex. A mountain lion would eat rabbits who eat berries, if there are no mountain lions to kill the rabbits, then the berries may be scarce
Explanation:
bc i know everthing
A sample of 0.600 mol of a metal M reacts completely with excess fluorine to form 46.8 g of MF2.?
a) How many moles of F are in the sample of MF2 that forms? (1.20 mol F)
b) How many grams of M are in this sample of MF2?
c) What element is represented by the symbol M? (Ca)
Answer:
See Explanation
Explanation:
Given:
moles M = 0.600 mole
moles F = excess (for rxn stoichiometry)
Formula Weight (F.Wt.) of F = 19 grams/mole (from Periodic Table)
Yield in grams = 46.8 grams (assuming theoritical yield)
Rxn: M + F₂ => MF₂
0.600mol Excess 0.600mol (1:1 rxn ratio for M:MF₂)
a. moles of F in MF₂ = 2(0.600) moles F = 1.2 moles F
b. mole weight MF₂ = 46.8g/0.600mol = 78g/mole
F.Wt. MF₂ = F.Wt. M + 2(F.Wt. F)
=> mass M = F.Wt. M = [F.Wt. MF₂ - 2(F.Wt. F)] = 78g/mol. - 2(19g/mol.)
= (78 - 38) grams/mole = 40 grams/mole
c. Calcium (Ca) has F.Wt. = 40 grams/mole (compared to Calcium on Periodic Table.
From the question, the metal is the limiting reactant and must be used to obtain the required results which are;
a) There are 1.20 mol F in MF2.
b) There are 40g of M in MF2.
c) M is calcium.
From the reaction equation;
M + F2 ----> MF2
Since the reaction is 1:1, 0.600 mol of MF2 is formed
Note that 1 mole of MF2 contains two moles of F and one mole of M
Hence, number of moles of F in MF2 = 2 * 0.600 mol = 1.20 mol F
Since 1 mole of M is contained in MF2, there are 0.600 moles of M in MF2.
If 1 mol of M forms 1 mole of MF2
And, 0.600 mol of M form 0.600 mol of MF2
Number of moles of MF2 = mass/molar mass
Number of moles of MF2 = 0.600 mol
Mass of MF2 formed = 46.8 g
Molar mass of MF2 = mass/Number of moles of MF2
Molar mass of MF2 = 46.8 g/0.600 mol
Molar mass of MF2 = 78 g/mol
Molar mass = Sum of Relative atomic mass of component atoms.
Hence;
78 = M + 2(19)
M = 78 - 2(19)
M = 40 g
The element must be calcium
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Scientists classify rocks mainly according to which feature?
their color
how they form
their hardness
where they are found
59. Which one has 0 dipole moment?
a. H2O2 b. Co2 c. HF
d. HBr
Answer:
the answer to this question is A H202
A hormone can have different effects in different species?
A. True
B. False
C. Cannot be decided
Answer:
true
Explanation:
it is because hormone determines various factors
help! help! plz give 4 different between orbit and orbital
Answer:
Differences between Orbit and Orbitals
Orbit
An orbit is the simple planar representation of an electron.
It can be simply defined as the path that gets established in a circular motion by revolving the electron around the nucleus
The shape of molecules cannot be explained by an orbit as they are non-directional by nature.
An orbit that is well-defined goes against the Heisenberg principle.
Orbital
An orbital refers to the dimensional motion of an electron around the nucleus in a three-dimensional motion.
An orbital can simply be defined as the space or the region where the electron is likely to be found the most.
The shapes of the molecules can be found out as they are directional by nature.
An ideal orbital agrees with the theory of Heisenberg’s Principles.
Find the mass of 2.40 moles of CO. gas..
The percentage by mass of oxygen in a compound containing potassium, chlorine, and oxygen was determined experimentally. The technique used follows. solid (KClo compound is weighed. Then it is heated in a crucible. The The solid decomposes to produce oxygen gas and a salt. Because the oxygen escaping, mass of the original solid decreases. From the mass of oxygen lost and mass is the the percentage by mass of oxygen in of the original the original compound is determined. KClyo. (s) salt (s) O (g A student performs five trials and determines the following by mass of oxygen in the compound (KCLO) by mass of oxygen Trial in the compound 38.933 38,940 38,892 38.900
a. Determine the average experimental percentage oxygen in the compound. by mass of 30.933
b. If the actual value of the percentage by mass ofoxygen in this compound is 39.13 determine the percentage error.
Answer:
See explanation
Explanation:
The percentage by mass of oxygen is defined as;
Mass of oxygen/ molar mass of the compound * 100/1
The average percentage by mass of oxygen = 38.933 + 38.940 + 38.871 + 38.892 + 38.900/5
The average percentage by mass of oxygen = 38.907
Percentage Error = (|accepted value – experimental value| \ accepted value) x 100%
Percentage Error = 39.13 - 38.907 / 39.13 * 100
Percentage Error = 0.57%
. Which state of matter has a defined volume but no defined shape?
HELPPPP PLEASE FAST
Answer:
liquid
Explanation:
it's not plasma, solid, or gas
so I think liquid
La fórmula molecular del pentano y del nonano son
Nose jajajajajaj si mr ayudas te ayudo
A small, rocky island is home to a community of organisms. They include birds,
insects, lichen, moss, shrubs, and small plants. Flooding during a storm damages the
ecosystem, except for the lichen and moss.
Two students observe the changes to the island community during and after the
storm. Chandra classifies the changes as primary succession, whereas Brenda
classifies them as secondary succession. Which argument is supported by the
evidence?
Brenda argument is supported.
Here moss and lichens are still there after the flood which will recolonize the colony once there.
What is primary successionPrimary succession is ecological succession that begins in essentially lifeless areas, such as regions in which there is no soil or where the soil is incapable of sustaining life.
What is secondary succession?It is a type of ecological succession in which plants and animals recolonize a habitat after a major disturbance such as a devastating flood, wildfire, landslide, lava flow, flood or human activity.
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How are stars and comets different?
A. A star has a solid rock and gas surface, while a comet has tail of dust and gas.
B. A star has a tail of dust and gas, while a comet has a solid rock surface.
C. A star is made up of burning gases, while a comet is made up of ice, gases, rocks, and dust.
D. A star is made up of ice, rocks, and dust, while a comet is made up of burning gases.
You and your family are on vacation in the mountains. You are trying to locate the campsite where you will be staying but you cannot get a signal. What is one reason why your GPS is not responding.
Answer:
A satellite may be malfunctioning.
Line of sight may be blocked.
low batteries in your GPS.
I'LL MARK YOU BRAINLIEST! Please help me balance these chemical reactions. (I'M NOT IN COLLEGE, I'M IN 10TH GRADE) Please help me
Answer:
1. H2 + Cl2 => 2HCl
2. Na2S + 2HCl => 2NaCl + H2S
3. 6HCl + 2Al => 2AlCl3 + 3H2
4. C3H8 + 5O2 => 3CO2 + 4H2O
5. C6H12O6 + 6O2 => 6CO2 + 6H2O
6. 4C12H23O11 + 49O2 => 48CO2 + 46H2O
7. 4NH3 + 7O2 => 4NO2 + 6H2O
8. 2Mg + 02 => 2MgO
hope it helps
A tank contains 10 liters of pure water. A solution of an unknown, but constant concentration of salt is flowing in at 0.5 liters per minute. The water is mixed well and drained at 1 liter per minute. After 20 minutes there are 10 grams of salt in the tank. (i) Give an adequate mathematical model for this scenario. Explain what each of your variables means. (ii) What is the concentration of the incoming salt solution
Answer:
i) ∴∫[tex]\frac{dA}{A}[/tex] = ∫ [tex]\frac{-1}{10} dt[/tex] ------ ( 1 )
ii) C = 4.303
Explanation:
Given data:
water in tank = 10 liters
concentration of salt flowing in = 0.5 liters/min
10 grams of salt is left in tank after 20 minutes
mixed water is drained at 1 liter per minute
i) Adequate mathematical model for the scenario
lets assume ; A( t ) amount of salt after t minute
A( t ) = 10grams where t = 20 minutes
differentiate A(t)
dA / dt = ( rate in ) - ( rate out )
= 0.5 * 0 - A/10
∴∫[tex]\frac{dA}{A}[/tex] = ∫ [tex]\frac{-1}{10} dt[/tex] ------ ( 1 )
ii) hence; In A = [tex]\frac{-1}{10} t + C[/tex] ----- ( 2 )
at t = 20 , A = 10grams
find C = In 10 + 2
= 2.303 + 2 = 4.303
back to ( 2 )
In A = [tex]\frac{-t}{10} + 4.303[/tex]
∴ A = e [tex]\frac{-t}{10} + 4.303[/tex]
In a reaction that produces carbon dioxide, the theoretical yield is 59 grams. During the experiment, the reaction actually produced 52.9 grams of carbon dioxide. Determine the percent yield.
Answer:
mole ratio, which is equivalent to a 1;1 mole ratio, to a gram ratio. This means that when the reaction consumes 84.03 g of carbon monoxide, it should theoretically produce 132.03 g of carbon dioxide. Use this gram ratio to calculate the theoretical yield for your reaction.
Explanation:
Ethane is a hydrocarbon with a formula of C2H6 . How many Carbon and Hydrogen atoms are contained within 3 molecules of ethane ?
Answer:
Within three molecules of Ethane, it would have 6 carbon, and 18 hydrogen atoms in it.
Explanation:
How does a lithium atom form the most stable ion?
Answer:
im absoulutely positive it is C
If a sample contains 70.0 % of the R enantiomer and 30.0 % of the S enantiomer, what is the enantiomeric excess of the mixture?
Answer:
the enantiomeric excess of the mixture is 40%
Explanation:
The computation of the enantiomeric excess of the mixture is shown below:
As we know that
[tex]= |\frac{R - S}{R + S} |\times 100\\\\= |\frac{70 - 30}{70 + 30}| \times 100\\\\= 40\%[/tex]
Hence, the enantiomeric excess of the mixture is 40%
Learning Task 4: Think of two animals that reproduce sexually. In the first
box, draw an animal that fertilization occurs inside the body. In the second
box, draw an animal that exhibits external fertilization.
please help for me
In the first box, you should draw a chicken. In the second box, you should draw a cow or a horse.
I hope it helps you!!!! :D
[ pls mark me brainliest i need one more to rank up tysm if u do ]
A balloon has been filled to a volume of 1.90 L with 0.2 mol of helium gas. If I add helium until
0.6 mol of helium is in the balloon, what is the new volume of the balloon?
0.63 L
5.7 L
15.8 L
0.06 L
Answer:0
.63
Explanation:
Many homes that are not
connected to public sanitary
sewers might dispose of
sewage using a(n)
Answer:
pump that is the answer hope its right
A hydrogen atom is removed from the first carbon atom of a butane molecule and is replaced by a hydroxyl group.
Required:
Draw the new molecule formed.
Answer:
See answer below
Explanation:
In this case, let's draw the butane molecule:
CH₃ - CH₂ - CH₂ - CH₃
According to what the exercise states, we removed an atom of hydrogen from the frist carbon. This could be any of the terminals. I'll grab the first from left to right.
CH₂⁺ - CH₂ - CH₂ - CH₃
When this happens, the atom of carbon is lacking one space and it forms a carbocation.
Followed this step, an hydroxile group replace the atom of hydrogen. The hydroxile is the OH, and when we have an alkane with an OH group in the molecule, we are actually converting this molecule into an alcohol, therefore the molecule formed is:
OH - CH₂ - CH₂ - CH₂ - CH₃Hope this helps
does warm air or cool air hold more humidity.
Answer:
warm
Explanation:
Write the line notation for a cell in which the cell reaction is as follow
H2 + I2 = 2 HI
Answer:
I2(g)/I^-(aq)//H2 (g)/H^+(aq)
Explanation:
Let us remember that in every redox reaction, a specie is oxidized and a specie is reduced.
This means that one specie looses electrons while the other species gains electrons.
Considering the overall reaction; H2 + I2 = 2 HI
Oxidation half equation;
H2 (g) ------> 2H^+(aq) + 2e
Reduction half equation;
I2(g) + 2e ------> 2I^-(aq)
Line notation;
I2(g)/I^-(aq)//H2 (g)/H^+(aq)