What is the pH of a solution made by adding 0.025 moles of and acid with a pKa = 4.3 to enough water to make 500.0 mL of solution? You wish to make 1.00 L of 50.0 mM phosphate buffer at pH 7.4. You ha
Answers
To solve these buffer-related questions, we'll need to use the Henderson-Hasselbalch equation, which relates the pH of a buffer solution to the pKa and the concentrations of the acid and its conjugate base:
pH = pKa + log([A-]/[HA])
Therefore, the pH of the solution is approximately 1.30.
To find the pH of a solution made by adding 0.025 moles of an acid with a pKa of 4.3 to enough water to make 500.0 mL of solution, we need to determine the concentration of the acid first.
Concentration of the acid = moles/volume
Concentration = 0.025 moles / 500.0 mL = 0.050 M
Since the acid is fully dissociated, the concentration of H+ ions is also 0.050 M. We can calculate the pH using the equation:
pH = -log[H+]
pH = -log(0.050)
pH ≈ 1.30
Therefore, the pH of the solution is approximately 1.30.
To make 1.00 L of a 50.0 mM phosphate buffer at pH 7.4 using the given compounds, we need to determine the volumes or masses of each compound required.
The Henderson-Hasselbalch equation for a phosphate buffer can be written as:
pH = pKa + log([H₂PO₄⁻]/[H₃PO₄])
Given:
pH = 7.4
pKa(H₃PO₄) = 2.12
pKa(H₂PO₄⁻) = 7.2
pKa(Na₂HPO₄) = 12.3
To achieve the desired pH, we need to choose the appropriate ratios of the acid (H₃PO₄) and its conjugate base (H₂PO₄⁻) using the Henderson-Hasselbalch equation.
Since the pH is higher than the pKa of H₃PO₄, we need to use a combination of H₃PO₄ and H₂PO₄⁻ to create a buffer.
To make 2.50 L of a 0.075 M phosphate buffer at pH 7.8 using H₃PO₄ (3.00 M) and NaOH (2.00 M), we need to determine the volumes of each solution required.
Given:
Desired volume = 2.50 L
Desired concentration = 0.075 M
pH = 7.8
pKa(H₃PO₄) = 2.12
pKa(H₂PO₄⁻) = 7.2
pKa(Na₂HPO₄) = 12.3
To achieve the desired pH, we need to choose the appropriate ratios of H3PO4 and its conjugate base H₂PO₄⁻ using the Henderson-Hasselbalch equation.
Since the pH is higher than the pKa of H₃PO₄, we need to use a combination of H₃PO₄ and H₂PO₄⁻ to create a buffer.
To calculate the volumes of each solution, we can use the Henderson-Hasselbalch equation and the equation for the buffer concentration:
[H₂PO₄⁻] = (Ka * [H₃PO₄]) / ([H+] - Ka)
[H₂PO₄⁻] = (\(10^(pKa - pH)\)* [H₃PO₄]) / (1 - \(10^(pKa - pH)\))
[H₂PO₄⁻] = (\(10^(7.2 - 7.8)\) * 0.075) / (1 - \(10^(7.2 - 7.8)\))
[H₂PO₄⁻] ≈ 0.00536 M
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The complete question is
What is the pH of a solution made by adding 0.025 moles of and acid with a pKa = 4.3 to enough water to make 500.0 mL of solution? You wish to make 1.00 L of 50.0 mM phosphate buffer at pH 7.4. You have 1.20 M H3PO4 pKa = 2.12, 1.75 M H₂NaPO4 pKa = 7.2, and solid Na2HPO4 pKa = 12.3. How much (either mL of grams) of which compounds should you use? You wish to make 2.50 L of 0.075 M phosphate buffer at pH 7.8. All you have is H3PO4 at 3.00 M, and NaOH at 2.00 M. How much (mL) of each do you need to use? See pKa values from the last question. This is similar to the acetic acid NaOH question we did in
Related Questions
A compound is analyzed and determined to be 30.4% nitrogen and 69.6%
oxygen. What is the empirical formula of the compound?
Answers
Answer:
NO2
Explanation:
The empirical formula represents the simplest whole number ratio of the elements in a compound. According to the question;
30.4% represents 30.4g of nitrogen
69.6% represents 69.6g of oxygen
First, we convert each mass value to mole by dividing by their respective molar masses as follows:
N = 30.4/14 = 2.17mol
O = 69.6/16 = 4.35mol
Next, we divide each mole value by the smallest (2.17)
N = 2.17/2.17 = 1
O = 4.35/2.17 = 2.0046
Approximately, the ratio of N to O is 1:2, hence, the empirical formula is NO2
What is the pOH of water?
Answers
Answer:
A. 7
(assuming the water is neutral)
viết cấu hình electron
Fe(z=26) Zn(z=30)
Cr(z=24) Cu(z=29)
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Answer:
i dont knowww bro lollll
consider a particular metal. at a certain temperature, t1, there is one vacancy for every 10,000 atoms. at a new temperature, t2, there is one vacancy for every 9,000 atoms. what increase in temperature is needed to create one vacancy for every 9,000 atoms (i.e., t2-t1)?
Answers
To find the increase in temperature needed to create one vacancy for every 9,000 atoms, we need to use the Arrhenius equation. The Arrhenius equation is used to determine the temperature dependence of reaction rates. It is given by the equation:
k = A * e^(-Ea/RT)
Where k is the rate constant, A is the pre-exponential factor, Ea is the activation energy, R is the gas constant, and T is the temperature.
In this case, we can rearrange the equation to solve for the temperature difference, t2-t1:
ln(k2/k1) = -Ea/R * (1/t2 - 1/t1)
We know that k2/k1 = 10,000/9,000 = 1.111. We also know that Ea and R are constants. Therefore, we can rearrange the equation to solve for the temperature difference:
t2-t1 = -Ea/R * (1/ln(1.111))
Using the values for Ea and R, we can plug them into the equation and solve for the temperature difference:
t2-t1 = -Ea/R * (1/ln(1.111))
t2-t1 = (-Ea/R) * (-9.2103)
t2-t1 = 9.2103 * Ea/R
Therefore, the increase in temperature needed to create one vacancy for every 9,000 atoms is 9.2103 * Ea/R.
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A student is building an electrical circuit. Which material should she choose for wires, and why.
Look at the screen shot
Answers
D. A metal such as copper, because its atom have very mobile electrons - A-p-e-x verified!
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What is a decay chain?
A. One element decaying into another, which decays into another
B. A list of radioactive substances organized by half-life times
C. An accumulation of particles emitted through radioactive decay
D. A list of radioactive substances organized by atomic weights
Answers
Answer:
A
Explanation:
A. One element decaying into another, which decays into another
Select the correct answer. Light ray A moves from air to water. Part of ray A is reflected at the air-water boundary. Which arrow in the image is the reflected ray? A picture shows a light ray A moving from air to water. Ray B moves from water to air. The rays C and D move down inside the water and the ray E moves along the surface of the water. A. B B. C C. D D. E
Answers
Answer:
The correct answer is A. B. The arrow in the image that represents the reflected ray is the one labeled "B," which shows the direction of the ray after it has bounced off the air-water boundary.
Ammonia (NH3) and formaldehyde (H2CO) each have three bonds around the central atom; however, their molecular shapes are different. Explain this observation.
Answers
The presence of the lone pair on nitrogen in NH3 explains why the molecule has a different shape from H2CO in which there is no lone pair
What is molecular shape?The molecular shape of a compound is determined by the number of electron pairs that surround the central atom in the molecule.
Let us also note that the presence of lone pairs distorts the shape of a molecule from the ideal prediction of the valence shell electron pair repulsion theory.
Thus, the presence of the lone pair on nitrogen in NH3 explains why the molecule has a different shape from H2CO in which there is no lone pair on the central atom.
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An endothermic reaction
OA. generates
OB. eliminates
OC. None of these
D. absorbs
energy.
Answers
Answer:
D) absorbs energy
What volume in liters, L, of solution should Sue prepare if she wants to make a 2.50 M solution using 75.0 grams, g, of potassium iodide, KI
Answers
Sue should prepare 0.750 L of solution.
To prepare a 2.50 M solution of potassium iodide using 75.0 g of the compound, Sue needs to first calculate the molar mass of KI, which is 166 g/mol. Then, she can use the formula M = n/V, where M is the molarity, n is the number of moles, and V is the volume in liters. By rearranging the formula, she can solve for V, which is V = n/M.
To find the number of moles, she can divide the mass by the molar mass: n = 75.0 g / 166 g/mol = 0.451 moles. Substituting these values, she gets V = 0.451 moles / 2.50 mol/L = 0.180 L. However, this is the volume needed for a 2.50 M solution.
To adjust the concentration to the desired value, she can use the formula M1V1 = M2V2, where M1 and V1 are the initial concentration and volume, and M2 and V2 are the final concentration and volume. Solving for V2, she gets V2 = M1V1 / M2 = 2.50 mol/L x 0.180 L / 0.750 mol/L = 0.600 L. Therefore, Sue should prepare 0.750 L of solution.
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Which scale for measuring temperature has zero as the point that water freezes?
Answers
Answer: Celsius scale
Explanation: The Celsius scale is based on water's freezing and boiling point under standard atmospheric conditions where water freezes at 0 °C and boils at 100 °C.
a 25.0ml sample of 0.125 m puradine is titrated with 0.100m hydrochloric acid. calculate the ph at each volume of added acid
Answers
To calculate the pH at each volume of added acid, we need to use the formula:
pH = -log[H+]
First, we need to determine the number of moles of puradine in the 25.0ml sample:
moles of puradine = volume of sample (in L) x molarity of puradine
moles of puradine = 0.025 L x 0.125 mol/L
moles of puradine = 0.003125 mol
Next, we can set up a table to calculate the pH at each volume of added acid:
Volume of added acid (mL) | Moles of HCl added | Total moles of H+ | pH
---------------------------------------------------------------------
0 | 0 | 0.003125 | 2.90
5 | 0.005 | 0.00363 | 2.44
10 | 0.01 | 0.004375 | 2.36
15 | 0.015 | 0.005125 | 2.28
20 | 0.02 | 0.005875 | 2.22
25 | 0.025 | 0.006625 | 2.16
To calculate the moles of H+ at each volume of added acid, we need to use the balanced chemical equation for the reaction between puradine and hydrochloric acid:
C5H4N4 + 4HCl → 4Cl- + C5H3N4H+
For every mole of HCl added, we get one mole of H+. Thus, the total moles of H+ at each volume of added acid can be calculated as follows:
Total moles of H+ = moles of puradine + moles of HCl added
Finally, we can calculate the pH at each volume of added acid using the formula:
pH = -log[H+]
Note that the initial pH of the puradine solution (at zero volume of added acid) is calculated using the Ka value for puradine (1.2 x 10^-5) and the Henderson-Hasselbalch equation. However, since the question only asks for the pH at each volume of added acid, we do not need to calculate the initial pH.
In summary, we can calculate the pH at each volume of added acid by setting up a table and using the formula pH = -log[H+]. The initial pH of the puradine solution can be calculated separately using the Henderson-Hasselbalch equation.
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How many grams of calcium chloride are needed to produce 10. 0 g of potassium chloride?
cacl2( aq) k2co3( aq) → 2kcl( aq) caco3( aq)
Answers
Answer:
7.44 grams CaCl2 will produce 10.0 grams KCl.
Explanation:
The equation is balanced:
I've repeated it here, with the elements corrected for their initial capital letter.
CaCl2( aq) K2CO3( aq) → 2KCl( aq) CaCO3( aq)
This equation tells us that 1 mole of CaCl2 will produce 2 moles of KCl.
If we want 10.0g of KCl, we need to convert that mass into moles KCl by dividing by the molar mass of KCl, which is 74.55 grams/mole.
(10.0 grams KCl)/(74.55 grams/mole) = 0.1341 moles of KCl.
We know that we'll need half that amount of moles CaCl2, since the balanced equation says we'll get twice the moles KCl for every one mole CaCl2.
So we'll need (0.1341 moles KCl)*(1 mole CaCl2/2moles KCl) = 0.0671 moles CaCl2.
The molar mass of CaCl2 is 110.98 grams/mole.
(0.0671 moles CaCl2)*(110.98 grams/mole) = 7.44 grams CaCl2
7.44 grams CaCl2 will produce 10.0 grams KCl.
How much heat is released when 5.0 g of hydrogen peroxide decomposes at constant pressure when enthalpy change is given as -196kj?
Answers
The Cyclohexane Ring Is Essentially Free Of Ring Strain Because Check All That Apply. There Are Neither Eclipsed Nor Gauche Interactions In ____
Answers
The cyclohexane ring is essentially free of ring strain because:
What is cyclohexane?
Cyclohexane is a cyclic hydrocarbon with the molecular formula C6H12. It is a colorless, flammable liquid that is commonly used as a nonpolar solvent in chemical reactions and as a starting material for the synthesis of other compounds. Cyclohexane is a cycloalkane, which means it contains a closed ring of carbon atoms.
There are no eclipsed interactions in the chair conformation of cyclohexane.There are no gauche interactions in the chair conformation of cyclohexane.The bond angles in the chair conformation of cyclohexane are close to the ideal tetrahedral angle of 109.5 degrees, which minimizes the angle strain in the molecule.The chair conformation of cyclohexane allows for maximum separation of the substituents on the ring, which minimizes the torsional strain in the molecule.All of these factors contribute to the stability of the chair conformation of cyclohexane and the absence of ring strain in the molecule.
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what is the volume of 0.284g of carbon dioxide at STP ??
Answers
Answer:
Explanatio
NCO2= 0, 248 /44= 0 ,005636
VCO2= 0,005636* 22,4= 0 ,126254545
reaction rates may be almost instantaneous or may be billions of year long. T/F
Answers
True. Reaction rates can vary significantly, ranging from almost instantaneous reactions to reactions that take billions of years to occur. The rate of a chemical reaction depends on several factors, including the nature of the reactants, their concentrations, temperature, pressure, and the presence of catalysts. These factors can greatly influence the speed at which reactions proceed.
The rate of a chemical reaction is a measure of how quickly reactants are converted into products. Different reactions exhibit varying rates, ranging from very fast reactions that occur within fractions of a second to extremely slow reactions that may take billions of years to complete.
The rate of a reaction depends on several factors. The nature of the reactants and their ability to interact and undergo chemical transformations play a significant role. Additionally, the concentrations of the reactants, temperature, pressure, and the presence of catalysts can also influence reaction rates.
For example, certain reactions, such as combustion reactions, can occur rapidly and almost instantaneously, releasing a large amount of energy. On the other hand, some geological processes, like the transformation of minerals or the decay of radioactive isotopes, can take billions of years to complete.
Therefore, it is true that reaction rates can range from nearly instantaneous to extremely long timescales, depending on the specific reaction and the conditions under which it occurs.
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Suppose 2,560 grams of low-level radioactive waste is buried at a waste disposal site. Assume that 10 grams of radioactive material gives off an acceptable level of radiation and that one half-life is 5.26 years. Write a paragraph in which you explain to townspeople how much time must pass before there is an acceptable ratiation level at the site.
Answers
However, keep in mind that 20 mSv per year is the recommended amount for any radiation worker and is still regarded quite safe. This is the most radiation most of us will ever be exposed to.
after 1st half life , remaining sample would be 100/2=50 g
after 2nd half life , remaining sample would be 50/2=25 g
after 3rd half life , remaining sample would be 25/2= 12.5 g
What is a radioactive material's half-life?The half-life of a radionuclide is the amount of time it takes for half of its radioactive atoms to decay. A decent rule of thumb is that you will have less than 1% of the initial quantity of radiation after seven half-lives. Click here to learn more about half life.
A short-term and whole-body dosage would result in rapid sickness, such as nausea and a reduction in white blood cell count, followed by death.
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42.08 years of time must pass before there is an acceptable radiation level at the site.
What is the half-life of a radioactive material?
The half life of a radioactive substance is the period of time during which its mass or number of atoms is decreased to half of what it was initially. The time it takes for a radioactive substance (or half of its atoms) to break down or transform into another substance is commonly used to define half-life.
Radioactivity, as its name suggests, is the act of generating radiation without any external cause. This is accomplished by an atomic nucleus that is unstable for whatever reason and "wants" to surrender some energy in order to change its configuration to one that is more stable.
After first half-life will remain 2560/2 i.e. 1280g of radioactive substance.
After second half-life will remain 1280/2 i.e. 640g
After 3rd half-life will remain 640/2 i.e. 320g
After 4th half-life will remain 160g
After 5th half-life will remain 80g
After 6th, 7th and 8th half-life will remain 40g, 20g and 10g respectively
It takes 8 half-lives to reach acceptable level of radiation i.e. 8*5.26 years
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Where do you think the energy we get in our lives come from?
Answers
As humans we get our energy from other sources such as plants or even other animals. This is by consuming nutrients such as protein, which is converted into energy.
hope this helps! :)
How many grams of sodium hydroxide (NaOH) do you need to make 6.5 L of 1.0M solution?
Answers
260grams
Explanations:The formula for calculating the moles of NaOH is expressed as
\(\begin{gathered} moles=molarity\times volume \\ moles\text{ of NaOH}=1.0M\times6.5L \\ moles\text{ of NaOH}=6.5moles \end{gathered}\)Determine the required mass of NaOH
\(\begin{gathered} Mass\text{ of NaOH}=moles\times molar\text{ mass} \\ Mass\text{ of NaOH}=6.5\cancel{moles}\times\frac{40g}{\cancel{mole}} \\ Mass\text{ of NaOH}=260grams \end{gathered}\)Hence the grams of sodium hydroxide (NaOH) you need to make 6.5 L of 1.0M solution is 260grams
I need help with these questions
Answers
The definition of astronomic bodies are indicated below with the sentences defining them.
What are astronomic bodies?Astronomic bodies are celestial objects that occur naturally in space.
Here are their definitions below:
a. Supernova exhibits strong gravitational pull such that no light can escape
b. A nebula a large cloud of gas or dust in space.
c. A white dwarf is what a medium-mass star becomes at the end of it's life.
d. Protostar is the earliest stage of a star's life.
e. Black dwarf is a star left at the core of a planetary nebula.
f. Neutron stars are the remains of a high mass star.
g. A supernova is what occurs when a red supergiant star explodes.
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Suppose that three isotopes of element X occur in nature as follows:
The relative atomic mass of the naturally occurring mixture of element X is
Answers
Answer:
107.5 amu
Explanation:
isotopes: fractional Wt Avg
isotopes: isotopic mass %Abundance abundance (amu)
X110 110 60 0.60 66.0
X105 105 30 0.30 31.5
X100 100 10 0.10 10.0
∑ atm mass contributions = 107.5 amu*
*amu = atomic mass units
PLS HELP ME WITH QUESTION 5 I NEED HELP ASAP
Answers
Answer:
30.5%
Explanation:
If you have a liquid that you suspect might be a mixture explain what you might do to find out if it is.
Answers
Answer:
add a substace devider
Explanation:
i forgot what it was called but there is a chemical that allows the substances to seperste and than you can test the substaces ph and what it is
What is the answer, with the correct number of significant figures, for the following calculation?
4.20 x 7.8760 / (325.6071 - 325.003)
A. 55
B. 54.7578
C. 54.758
D. 54.75782
E. 54.8
Answers
Answer: The correct answer will be,
Explanation:Significant figures : The figures in a number which express the value -the magnitude of a quantity to a specific degree of accuracy is known as significant digits.
The rule apply for the addition and subtraction is :
The least precise number present after the decimal point determines the number of significant figures in the answer.
The given expression is:
In the given expression, 4.392 has 4 significant figures, 102.40 has 5 significant figures and 2.51 has 2 significant figures. From this we conclude that least precise number present after the decimal point is 2.
Thus, the answer will be
Which happens during crossing over?
Two sex cells join together and combine DNA.
Genes are exchanged between two alleles.
Genes are exchanged between two egg cells.
Chromosomes line up randomly during metaphase I.
Answers
Answer:
Chromosones line up randomly during Metaphase |
Explanation:
Answer:
answer is d
Explanation:for all you edge 2020 people :)
If you can solve both
Will mark brainly
ASAP
Answers
Answer:
1. answer is subcutaneous tissue 2. answer is spleen
Explanation:
The subcutis is also known as the hypodermis or subcutaneous layer, and functions as both an insulator, conserving the body's heat, and as a shock-absorber, protecting the inner organs.
Excretory Organs. Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. Together, these organs make up the excretory system.
Answer:
the answer is Subcutaneous Tissue
Explanation:
and the second one is Intestine
Find the volume of 53.5 g of O2 at 30.1°C and 110.0 kPa. Round to the nearest tenth.
Answers
The volume of 53.5 g of O₂ at 30.1°C and 110.0 kPa is 1 m³ approximately
The Charles Law: What is it explained?According to Charles' Law, while pressure is maintained constant, the volume of a given amount of gas varies in direct proportion to the absolute temperature of the gas. The Kelvin scale is used to measure temperature to determine the absolute temperature.
To find the volume of a gas, we can use the Ideal Gas Law:
PV = nRT
where P is the pressure of the gas, V is the volume of the gas, n is the number of moles of gas, R is the universal gas constant, and T is the temperature of the gas in Kelvin.
First, we need to convert the given temperature of 30.1°C to Kelvin:
T = 30.1°C + 273.15 = 303.25 K
Next, we need to determine the number of moles of O₂ present. We can use the molar mass of O₂ to convert from grams to moles:
molar mass of O₂ = 32.00 g/mol
moles of O₂ = 53.5 g / 32.00 g/mol = 1.671875 mol
Now we can rearrange the Ideal Gas Law to solve for V:
V = nRT / P
V = 1.671875 × 8.3145 × 303.25 /110 k × 1000 Pa / kPa
V = 0.062878 m³
Finally, we round the answer to the nearest tenth: (rounded to one decimal place) V = 1 m³
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What is the mass (in grams) of 4.5 x 10^23 units of NaCl?
could you also explain?
Answers
Answer:
43.7 g
Explanation:
unit mass of NaCl = (23 + 35.5) u = 58.5 u
58.5 is the mass of one unit formula of NaCl (since NaCl is not a molecular compound)
1 u = 1.661×10^-24 g
if 1 unit formula of NaCl has 58.5 u, then 4.5×10²³ units of NaCl will have:
58.5 u × (1.661×10^-24 g/1 u) × 4.5×10²³ = 43.7 g
In paragraph 2, attraction and repulsion refer to _____.
A electric and magnetic fields
B atomic theories
C tiny particles
D solid atoms
Answers
Answer:
I guess the answer is b.atomic theories