One liter of a 0.1M Tris buffer (pKa=8.3) is adjusted to a pH of 2.0. a. What are the concentrations of the conjugate base and weak acid at this pH? b. What is the pH when 1.5mL of 3.0M HCl is added to this buffer? Is Tris a good buffer at this pH? Why? c. What is the pH when 1.5mL of 3.0M NaOH is added to this buffer?
Answer:
a. [Weak acid] = 0.099999949M
[Conjugate base = 5.0119x10⁻⁸M
b. pH = 1.84. Is not a good buffer
c. pH = 6.97
Explanation:
a. To find pH of the buffer we must use Henderson-Hasselbalch formula:
pH = pKa + log [Conjugate base] / [Weak acid]
2.0 = 8.3 + log [Conjugate base] / [Weak acid]
5.01x10⁻⁷ = [Conjugate base] / [Weak acid] (1)
As concentration of the buffer is 0.1M = [Conjugate base] + [Weak acid] (2)
Replacing (2) in (1):
5.01x10⁻⁷ = 0.1M - [Weak acid] / [Weak acid]
5.01x10⁻⁷ [Weak acid] = 0.1M - [Weak acid]
[Weak acid] = 0.099999949M
[Conjugate base] = 5.0119x10⁻⁸M
b. The conjugate base reacts with the HCl. Moles of HCl are:
1.5x10⁻³L * (3.0mol / L) = 4.5x10⁻³ moles HCl
As the conjugate base contains just 5x10⁻⁸ moles. Almost all HCl doesn't react and pH =
[H⁺] = 4.5x10⁻³ moles + 1x10⁻² moles (Initial moles H⁺) / L = 0.0145M
pH = -log [H⁺]
pH = 1.84
As the concentration of the conjugate base is <<< than weak acid. In this pH, Tris is not a good buffer. As general rule a good buffer works pH between pKa ± 1.
c. Now, NaOH reacts with the weak acid producing conjugate base.
The new moles are:
[Weak acid] = [Weak acid] = 0.099999949M - 4.5x10⁻³ = 0.0955
[Conjugate base] = 5.0119x10⁻⁸M + 4.5x10⁻³ = 4.5x10⁻³
pH = pKa + log [Conjugate base] / [Weak acid]
pH = 8.3 + log [4.5x10⁻³] / [0.0955]
pH = 6.97
Following are the response to the given points:
For question a)
The concentration of Tris buffer [tex]\text{(Tris buffer)} = 0.1\ M[/tex]
Using formula:
[tex]\text{[ Tris buffer ] = [ Conjugate base ] + [ Acid ]}[/tex]
[tex]0.1 M = \text{ Conjugate base +Acid } \\\\ \text{Acid} = 0.1\ M - \text{ Conjugate base } .............(a)[/tex]
Using the Henderson-Hasselbalch equations
[tex]\to pH = pKa + \log \frac{\text{ Conjugate base }}{ Acid}\\\\\to 2.0 = 8.3 + \log \frac{\text{ Conjugate base }}{ Acid}\\\\\to \log \frac{\text{ Conjugate base }}{ Acid} = 2.0 - 8.3\\\\\to \log \frac{\text{ Conjugate base }}{ Acid} = - 6.3\\\\\to \frac{\text{ Conjugate base }}{ Acid}= 10-6.3\\\\\to \frac{\text{ Conjugate base }}{ Acid} = 5.01 \times 10^{-7}\\\\\to \text{Conjugate base} = 5.01 \times 10^{-7} \times \ Acid ..............(b)[/tex]
Putting the value of equation (b) in equation (a):
[tex]\text{Acid } = 0.1\ M - 5.01 \times 10^{-7}\\\\\text{Acid } = 0.1 M \ ( approx.)[/tex]
from equation (b)
[tex]\to \text{Conjugate base} = 5.01 \times 10^{-7} \times 0.1\ M= 5.01 \times 10^{-8}\ M\\\\[/tex]
Therefore,
[tex]\to \text{Acid} = 0.1\ M\\\\ \to \text{Conjugate base} = 5.01 \times 10^{-8}\ M[/tex]
For question b)
[tex]\to \text{Number of moles of HCl} = 3.0\ M \times 0.00152\ L= 0.0045 \ moles\\\\\to \text{Number of moles Conjugate base in 1 L of buffer} = 5.01 \times 10^{-8}\ M \times 1\ L = 5.01 \times 10^{-8}\ moles\\\\ \to \text{Number of moles of weak acid} = 0.1\ M \times 1\ L = 0.1\ moles\\\\[/tex]
Now we need all the conjugate bases for neutralizing the [tex]HCl[/tex]
therefore
Calculating the molarity of [tex]HCl[/tex] in the solution [tex]= \frac{0.0045\ moles}{1\ L} = 0.0045\ M[/tex]
[tex]\to H^+ \ in \ HCl = 0.0045 \ M\\\\p_H = 2.0\\\\\therefore \\\\ H^+ \ in \ buffer = 10^{-2}\ M = 0.01\ M \ ( \because \ p_H = - \log [ H^+]\ and\ [ H^+ ] = 10-p_H )[/tex]
Now Total concentration of [tex]H^+ \ i.e\ [H^+][/tex]
[tex]\to Total = 0.0045 + 0.01 = 0.0145\ M\\\\\to pH = - \log 0.0145\\\\\to pH = - ( - 1.84 )\\\\\to pH = 1.84\\\\[/tex]
For question c)
Number of moles of [tex]NaOH = 3.0 \ M \times 0.00152\ L= 0.0045\ moles\\\\[/tex]
[tex]\to \text{Number of moles Conjugate base ( say A-) in 1\ L of buffer} = 5.01 \times 10^{-8}\ M \times 1 \ L = 5.01 \times 10^{-8}\ moles \\\\ \to \text{Number of moles of weak acid ( say HA )} = 0.1\ M \times 1\ L = 0.1\ moles[/tex]
Now ICF table is :
[tex]HA + OH^- \longrightarrow A^- + H_2O[/tex]
[tex]\text{I 0.1 mol 0.0045 mol 5.01 x 10-8 mol}\\\\\text{C - 0.0045 mol - 0.0045 mol + 0.0045 mol}\\\\\text{F 0.0955 mol 0 mol 0.0045 mol ( approx. )}\\\\[/tex]
Using Henderson-Hasselbalch:
[tex]\to pH = 8.3 + \log \frac{0.0045}{ 0.0955} \\\\\to pH = 8.3 + \log 0.04712\\\\\to pH = 8.3 - 1.3268\\\\\to pH = 6.97[/tex]
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What is the partial pressure of water vapor in an air sample when the total pressure is 1.00 atm, the partial pressure of nitrogen is 0.79 atm, the partial pressure of oxygen is 0.20 atm, and the partial pressure of all other gases (except the water) is 0.0044 atm?
An unknown element X has the following isotopes: ⁵²X (79.50% abundant), ⁴⁹X (8.00% abundant), ⁵⁰X (12.50% abundant). What is the average atomic mass in amu of X?
Answer:
51.51 amu .
Explanation:
The atomic mass 52 amu has percentage of 79.5%
The atomic mass 49 amu has percentage of 8%
The atomic mass 50 amu has percentage of 12.5 %
Average atomic pass will be weighted average of their atomic weights
= 52 x .795 + 49 x .08 + 50 x .125
= 41.34 + 3.92 + 6.25
= 51.51 amu .
What is something a scientist could add to or subtract from an unknown substance that will always reveal information about the physical and/or chemical properties of the substance?(1 point) A. heat B. light C. iodine D.vinegar
PLEASSSSSSSSE HELP IMMEDIAATLYYYYYY.......
Yeah! I have the same question!!! I think it is heat.
Give the names and charges of the cation and anion in each of the following compounds:________.
(a) CuS, (b) Ag2SO4, (c) Al(ClO3)3, (d) Co(OH)2 and (e) PbCO3
Answer:
(a) [tex]Cu^{2+}S^{2-}[/tex]: copper (II) sulfide or cupric sulfide.
(b) [tex]Ag^+_2(SO_4)^{2-}[/tex]: silver sulfate.
(c) [tex]Al^{3+}(ClO_3)_3^-[/tex]: aluminum chlorate.
(d) [tex]Co^{2+}(OH)^-_2[/tex]: cobalt (II) hydroxide.
(e) [tex]Pb^{2+}(CO_3)^{2-}[/tex]: lead (II) carbonate.
Explanation:
Hello,
In this case, we proceed by exchanging the subscripts between the cation and anion for each case as follows:
(a) CuS: cation is cupper (II) and anion is sulfide, thus the name is copper (II) sulfide or cupric sulfide.
[tex]Cu^{2+}S^{2-}[/tex]
(b) Ag₂SO₄: cation is silver ion and anion is sulfate, thus the name is silver sulfate.
[tex]Ag^+_2(SO_4)^{2-}[/tex]
(c) Al(ClO₃)₃: cation is aluminum ion and anion is chlorate, thus the name is aluminum chlorate.
[tex]Al^{3+}(ClO_3)_3^-[/tex]
(d) Co(OH)₂: cation is cobalt (II) and anion is hydroxide, thus the name is cobalt (II) hydroxide.
[tex]Co^{2+}(OH)^-_2[/tex]
(e) PbCO₃: cation is lead (II) and anion is carbonate, thus the name is lead (II) carbonate.
[tex]Pb^{2+}(CO_3)^{2-}[/tex]
Regards.
Dynamic equilibrium between liquid and gas is established when __________ . a. the vapor pressure of the liquid equals the external pressureb. the liquid and vapor are at the same temperaturec. a liquid vaporizes and condenses at the same rated. the liquid is entirely evaporated
Answer:
The correct answer is option c. "a liquid vaporizes and condenses at the same rate"
Explanation:
In chemistry, dynamic equilibrium is defined as a state where the reaction rate of a forward reaction is equal to the reaction rate of the backward reaction. In this case, the reactions that participate in the system are the vaporization of a liquid and the condensation of a gas. Therefore, dynamic equilibrium is established when a liquid vaporizes and condenses at the same rate.
What is the mass, in grams, of a cube of copper that has a volume of 62.2 cm3?
) Copper density= 8.96 g/cm³ Copper volume= 51.3c.m.3 Copper density = M/V8.96= M/51. M= 459.68g.m.
Draw the structure of 2,4,4,5-tetramethyl-2-hexene.
Answer:
The answer to your question is given below
Explanation:
2,4,4,5-tetramethyl-2-hexene.
To draw the structure of the above compound, we must bear the following in mind:
1. The compound is an alkene i.e it contains carbon to carbon double bond (C=C)
2. The parent name of the compound is hexene i.e it contain 6 carbon atoms.
3. The double is located at carbon 2.
4. The substituent group attached to the compound is methly.
5. There are four methly group attached to the compound of which one is located at carbon 2, two at carbon 4 and one at 5.
With the above information, we can easily draw the structure of the compound.
Please see attached photo for the structure of the compound.
Mr. Hall was conducting an experiment. He dissolved an unknown
ubstance in water. He performed multiple trials while varying the
emperature. What is the independent variable in his experiment?
a. The unknown substance, because it's the only thing he changed
b.The temperature, because it's the only thing he changed
Answer:
a
Explanation:
How do humans affect sea turtles, seabirds and other marine animals?
Answer:
Fish, marine mammals and seabirds are being injured and killed by plastic corruption /pollution, and it is believed that 700 species could go deceased because of it. ... Losses are generally influenced by the ingestion of plastics, starvation, suffocation, virus, drowning and entrapment.
You can thank me and google
In a coffee cup calorimeter, 100.0 mL of 1.0M NaOH and 100.0 mL of 1.0M HCl are mixed. Both solutions were originally at 24.6 degrees Celsius. After the reaction, the final temperature is 31.3 degrees Celsius. Assuming that all the solution have a density of 1.0g/cm3 and a specific heat capacity of 4.18 J/oCg, calculate the enthalpy change for the neutralization of HCl by NaOH. Assume that no heat is lost to the surroundings or to the calorimeter.
Answer:
56.0kJ/mol
Explanation:
The reaction of NaOH with HCl is:
NaOH + HCl → H₂O + NaCl + ΔH
Where ΔH is the heat of reaction that is released per mole of reactants,
The moles that reacts are:
100mL = 0.1L * (1mol / L) = 0.1 moles reacts
To find the heat released in the coffee cup calorimeter, you use the equation:
Q = m×ΔT×C
Where Q is heat released,
m is mass of the solution
ΔT is change in temperature (Final temperature - Initial temperature)
C is specific heat of the solution (4.18J/g°C)
Mass of the solution is:
100mL + 100mL = 200mL
Density of the solution is 1.0g/mL. The mass is 200g
Change in temperature is 31.3°C - 24.6°C = 6.7°C
Replacing:
Q = m×ΔT×C
Q = 200g×6.7°C×4.18J/g°C
Q = 5601.2J
This is the heat released per 0.1mol. The heat released per mole (Enthalpy change for the neutralization of HCl by NaOH is:
5601.2J / 0.1 moles = 56012J / mol =
56.0kJ/mol
Write the electron configuration for the following elements. (1) Neon, (2) Zinc, (3) Tungsten, (4) Magnesium
Explanation:
Hey there!!
We generally use s,p,d,f formula.
So, let's do with it.
1.Neon
Atomic no. = 10
So, Its electronic configuration is;
[tex] = 1 {s}^{2} .2 {s}^{2} 2 {p}^{6} [/tex]
2.Zinc.
Atomic no. = 30
So, it's electronic configuration is;
[tex] = 1 {s}^{2} 2 {s}^{2} 2 {p}^{6} 3 {s}^{2} 3 {p}^{6} 4 {s}^{2} 3 {d}^{10} [/tex]
3. Tungsten.
Atomic no. = 74.
So, it's electronic configuration is;
[tex] = 1 {s}^{2} 2 {s}^{2} 2 {p}^{6} 3 {s}^{2} 3 {p}^{6} 4 {s}^{2} 3 {d}^{10}4 {p}^{6} 5 {s}^{2} 4 {d}^{10} 5 {p}^{6} 6 {s}^{2} 4 {f}^{14} 5 {d}^{4} [/tex]
4. Magnesium.
Atomic no. = 12
So, the electronic configuration is ;
[tex] = 1 {s}^{2} 2 {s}^{2} 2 {p}^{6}3 {s}^{2} [/tex]
Hope it helps...
HELP ME PLEASE, what kind of cell is?
Answer:
Explanation:
Plant cell because its shape is rectangular
Determine whether each of the descriptions of matter describes:
1. a heterogeneous mixture,
2. a homogeneous mixture,
3. a pure substance.
4. no correct response
a. two substances present; two phases present
b. two substances present; one phase present
c. one substance present; one phase present
d. one substance present; two phases present
Answer:
a heterogeneous mixture,-two substances present; two phases present
a homogeneous mixture- two substances present; one phase present
a pure substance- one substance present- one phase present
no correct response-one substance present; two phases present
Explanation:
When two substances are mixed, the mixture may be homogenous or heterogeneous. If a mixture is homogenous, then the two substances form a single phase, e.g ethanol and water.
On the other hand, a heterogeneous mixture is divided into two distinct phases, e.g kerosene and water mixture.
A single substance can only give one phase, no substance can simultaneously give two phases of the same substance in the same physical state.
Similarly, a pure substance always consists of a single phase.
Convert 1663.5 g to mg
Answer:
It will be 1663500mg
Explanation:
Are the bonds that chlorine forms with sodium (to form NaCl) and with carbon (to form CCl4) the same in both compounds?
Answer:
No, NaCl is formed by an ionic bond, and CCl4 would be formed by covalent bonds.
Explanation:
NaCl is an ionic bond because of their opposite charges while carbon and chlorine are sharing their electrons making it a covalent bond.
Taking into account the definition of ionic and covalent bond, the bonds that chlorine forms with sodium (to form NaCl) and with carbon (to form CCl₄) are different in both compounds.
Ionic bondAn ionic bond is a type of chemical bond that occurs when one atom gives up an electron to the other, in order for both to achieve electronic stability.
This union normally occurs between metal and nonmetal elements with different electronegativity, which means that the elements have different capacity to attract electrons.
In other words, an ionic bond is produced between metallic and non-metallic atoms, where electrons are completely transferred from one atom to another. During this process, one atom loses electrons and another one gains them, forming ions. Usually, the metal gives up its electrons forming a cation to the nonmetal element, which forms an anion.
Covalent bondThe covalent bond is the chemical bond between atoms where electrons are shared, forming a molecule. Covalent bonds are established between non-metallic elements, such as hydrogen H, oxygen O and chlorine Cl. These elements have many electrons in their outermost level (valence electrons) and have a tendency to gain electrons to acquire the stability of the electronic structure of noble gas.
Bonds of NaCl and CCl₄In the case of NaCl, Na is a metal while Cl is a nonmetal. So NaCl is an ionic bond.
On the other hand, in the case of CCl₄ both C and Cl are two non-metallic elements. So CCl₄ is a covalent bond.
In summary, the bonds that chlorine forms with sodium (to form NaCl) and with carbon (to form CCl₄) are different in both compounds.
Learn more about
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covalent bond:
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Which of the following is the basis for arranging the elements in the modern periodic table?
Answer:
The correct answer is - ascending order of atomic numbers in period and similar characters in groups.
Explanation:
The modern periodic table is arranged in periods and groups. In periods the arrangement of the elements are on the basis of the increasing order of atomic numbers.
In groups of the periodic table, elements are arranged on the basis of the similar characters of the elements and number of electrons in outer shell of the elements. The elements in the Modern Periodic Table are arranged in 7 Periods and 18 Groups.
Thus, the correct answer is - ascending order of atomic numbers in period and similar characters in groups.
please answer this question
Answer:
1. False, water can't because its liquid
2. True, it dissolves more substances than any other liquid
3. False,stirring speeds up the rate of dissolving
Hope this helped
An unknown acid solution has PH 3.4. 66% of the acid is ionized. Whats the pka?
Answer:
[tex]pKa=3.58[/tex]
Explanation:
Hello,
In this case, since the pH defines the concentration of hydrogen:
[tex]pH=-log([H^+])[/tex]
[tex][H^+]=10^{-pH}=10^{-3.4}=3.98x10^{-4}[/tex]
And the percent ionization is:
[tex]\% \ ionization=\frac{[H^+]}{[HA]}*100\%[/tex]
We compute the concentration of the acid, HA:
[tex][HA]=\frac{[H^+]}{\% \ ionization}*100\%=\frac{3.98x10^{-4}}{66\%} *100\%\\\\[/tex]
[tex][HA]=6.03x10^{-4}[/tex]
Thus, the Ka is:
[tex]Ka=\frac{[H^+][A^-]}{[HA]}=\frac{3.98x10^{-4}*3.98x10^{-4}}{6.03x10^{-4}}\\ \\Ka=2.63x10^{-4}[/tex]
So the pKa is:
[tex]pKa=-log(Ka)=-log(2.63x10^{-4})\\\\pKa=3.58[/tex]
Regards.
In an NMR experiment, shielding refers to the reduced impact of the ______on a nucleus due to the presence of ______around the nucleus. Shielding can be_____by the presence of more electronegative groups around the nucleus. A shielded nucleus appears further ______ whereas a deshielded nucleus appears further _____in an NMR spectrum.
Answer:
In an NMR experiment, shielding refers to the reduced impact of the APPLIED MAGNETIC FIELD on a nucleus due to the presence of ELECTRON DENSITYaround the nucleus.
Shielding can be DECREASED by the presence of more electronegative groups around the nucleus.
A shielded nucleus appears further UPFIELD whereas a deshielded nucleus appears further downfield in an NMR spectrum.
Explanation:
1 There is reducece because alot of the electronegative atom binds more and thus reduce the electron density around the nucleus.
While a reduction in electron density bring about more nuclear magnetic field thus it resonates at higher frequency resulting downfield peak.
When There is reduce because a lot of the electronegative atom binds more and also that thus reduces the electron density around the nucleus.While a reduction in electron density brings about more nuclear magnetic field thus it resonates at higher frequency resulting downfield peak.
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What happens to these physical properties as the strength of intermolecular forces increases?Increase or decrease?a) melting point - increasesb) vapor pressure-increasesc) boiling point- increasesd) viscosity - decreasese) surface tension - decreases
Boiling Point, Melting Point, Viscosity, Surface Tension. Decrease: Vapor Pressure.
Draw 1,2,3,4,5,6-hexachlorocyclohexane with :
a. all the chloro groups in axial positions.
b. all the chloro groups in equatorial positions.
Answer:
This is required answer.
Explanation:
Given that,
1,2,3,4,5,6-hexachlorocyclohexane
(a). We need to draw 1,2,3,4,5,6-hexachlorocyclohexane with all the chloro groups in axial positions
Using given data
We draw 1,2,3,4,5,6-hexachlorocyclohexane with all the chloro groups in axial positions.
When we say that all the chloro groups in axial position that means axial bonds are vertical.
(b). We need to draw 1,2,3,4,5,6-hexachlorocyclohexane with all the chloro groups in equatorial positions
Using given data
We draw 1,2,3,4,5,6-hexachlorocyclohexane with all the chloro groups in equatorial positions.
When we say that all the chloro groups in equatorial position that means axial bonds are horizontal.
Hence, This is required answer.
a rectangle solid has a length of 3cm a height of 4 centimeters and a width of 5cm what is the solid’s volume?
Answer:
Explanation:
volume = 60cm^3
If u burn paper in the jar, is it the same mass as before u burn it or less or more.
Answer: the mass will be same
Answer:
the mass wouldnt be the same because of the ashes in the jar
Explanation:
Classify each of the following as a pure substance or a mixture. If a mixture, indicate whether it is homogeneous or heterogeneous:_______. (a) rice pudding, (b) seawater, (c) magnesium, (d) crushed ice.
Answer:
a) Heterogeneous mixture (b) Homogenous mixture (c) Pure substance (d) Pure substance
Explanation:
Homogenous mixtures contains mixture of substances with similar proportions while Heterogenous mixture contains substances with a varying proportion.
Which of the following is true in regard to a proton?Choose one or more:A. A proton has a 1+ charge.B. A neutral atom must have an equal number of protons and neutrons.C. A proton has a mass of about 1.0 amu.D. A proton has a 1- charge.E. The number of protons determines the identity of an element.
Answer:
1. A PROTON HAS A +1 CHARGE
2. A PROTON HAS A MASS OF ABOUT 1.0 amu
3. THE NUMBER OF PROTONS DETERMINES THE IDENTITY OF AN ELEMENT
Explanation:
The proton is one of the three particles that make up the atom. Proton is a positively charge particle with a +1 charge. It neutralizes the negative charge of the electrons outside of the nucleus of the atom as the proton are located inside the nucleus of the atom. Proton has a mass of 1.0 amu which is about 1.67 * 10^-27 kg. The addition of the proton and the neutrons gives the molar mass of the atom.
Also, the identity of the cell that is the atomic number which gives the position of the element in the periodic table and also shows the individual characteristics of the atoms is determined by the number of protons in the nucleus of the atoms.
All the above options are true in regard to a proton.
Speed = Acceleration x Time
30. If an object accelerates at 5 m/s2 for
4 seconds, how fast will it be going?
EXPLAIN How did energy change form in the calorimeter lab?
As the food burned, thermal chemical nuclear energy was transformed into
thermal chemical | nuclear energy. Thus, a form of kinetic | potential energy was
converted to a form of kinetic potential energy.
Answer:
Chemical energy is converted into thermal and mechanical energy while kinetic energy into potential energy.
Explanation:
As the breakdown of food started, the chemical energy present in the food substances converted into thermal energy and mechanical energy. Thermal or heat energy is used to maintain the body's temperature while mechanical energy is used in other activities such as movement of muscles. Kinetic energy is also converted into potential energy when the object moves from top of a place such as hill.
As the food burned, chemical energy was transformed into thermal energy. Thus, a form of potential energy was converted to a form of kinetic energy.
Hope I helped! :)
Ap chem, please help with number 31!!
Answer:
this old man looks so weird ..
Explanation:
but i m sorry .....u know the reason very well
do u wanna be my friend .
How can we be safe in a science laboratory
Answer:
We can be safe in a science laboratory by following all directions and wearing gloves, goggles to protect ourselves.
Explanation:
If we don't follow the rules then we might cuase a problem that we didn't want to happen and we need to wear protective gear because we need to stay safe