Which acid and its conjugate base would be the best buffer at pH=7.5?
Answer:
HEPES.
Explanation:
Hello,
In this case, considering the given options, and the pH requirement of 7.5, considering the Henderson-Hasselbach equation:
[tex]pH=pKa+log(\frac{[base]}{[acid]})[/tex]
The best buffer is that having the closest pKa to the required pH, thus, for the given Ka, we obtain:
[tex]pKa_{MES}=-log(Ka_{MES})=-log(7.9x10^{-7})=6.10\\\\pKa_{HEPES}=-log(Ka_{HEPES})=-log(3.2x10^{-8})=7.49\\\\pKa_{Formic \ acid}=-log(Ka_{Formic \ acid})=-log(1.8x10^{-4})=3.74\\\\pKa_{Acetic\ acid}=-log(Ka_{Acetic\ acid})=-log(1.8x10^{-5})=4.74\\\\pKa_{Tris}=-log(Ka_{Tris})=-log(6.3x10^{-9})=8.2[/tex]
Therefore, the best buffer is the HEPES since its pKa is almost the required pH.
Regards-
Suppose you are titrating a sulfuric acid solution of unknown concentration with a sodium hydroxide solution according to the equation H 2 S O 4 + 2 N a O H ⟶ 2 H 2 O + N a 2 S O 4 If you require 29.09 mL of 0.639 M N a O H solution to titrate 213.8 mL of H 2 S O 4 solution, what is the concentration of the H 2 S O 4 solution?
Answer:
Explanation:
H ₂ S O ₄ + 2 N a O H ⟶ 2 H ₂ O + N a ₂ S O ₄
29.09 mL of 0.639 M N a O H is mixed with 213.8 mL of H ₂ S O ₄
Let the concentration of H ₂ S O ₄ be S₂ .
In terms of normal or equivalent solution is will be 2 N solution
From the formula S₁ V₁ = S₂ V₂
= 29.09 x .639 = 213.8 x S₂
S₂ = .087 N solution
In terms of molar solution it will be .087 / 2 M
= .0435 M
All measurements contain errors. Averaging the measurements reduces the error. A graph can also reduce error when the line is drawn through the center of the data. A student measured the mass and volume of 5 different pieces of the same metal, plotted the data and obtained a slope of 8.90 g/mL. How did you know that the metal was copper and not nickel? (Describe a different way to identify that the metal is copper).
Answer:
See explanation
Explanation:
The slope of a graph in which mass was plotted against volume is the density of the object. Density of objects have been measured and recorded in standard handbooks for the purpose of reference. If the density of an unknown substance is measured, it can now be compared with the density of known substances recorded in standard handbooks such as the handbook of physics and chemistry. By so doing, the unknown substance can be identified.
According to standard handbooks, the density of copper is 8.96 g/ml while that of nickel is 8.908 g/ml. If the average slope obtained is around 8.96 g/ml, then the metal is copper and not nickel.
An alternative to this method is to measure the refractive index of the piece of metal and compare the average values observed with the contents of standard handbooks in order to identify the unknown metal.
The element oxygen has valence electrons
Answer:
it’s electron configuration is 1s^2 2s^2 2p^4. To determine valence electrons, add the outermost s and p orbitals. In an oxygen atom, 8 electrons are present. Electron present in the first shell (n=1) 2n^2=2 (1)^2=2 (1)=2.
What is the mass of 12.83 mL of acetic acid (98% wt/wt)?
Answer:
The mass of the acetic acid is 13.5 g
Explanation:
Given;
weight percent of the acetic acid (ratio of solute to total solution), w/w = 98 %
volume of acetic acid, v = 12.83 mL
density of acetic acid, ρ = 1.05 g/mL
density is given by;
density = mass / volume
mass = density x volume
mass of the acetic acid in 12.83 mL = 1.05 g/mL x 12.83 mL
mass of the acetic acid in 12.83 mL = 13.5 g
Therefore, the mass of the acetic acid is 13.5 g
What mass of sodium hydroxide will completely neutralize 2.5 mol of sulfuric acid?
Given :
2.5 mole of Sulfuric acid [tex]( H_2SO_4 )[/tex] .
To Find :
Mass of sodium hydroxide will completely neutralize 2.5 mol of sulfuric acid
Solution :
Let us assume volume of water be 1 L .
Now , we know , to neutralize 1 mole of sulfuric acid we need 2 moles of NaOH .
So , for 2.5 mole sulfuric acid required 5 mole of NaOH .
Moles of NaOH ,
[tex]n=M\times Volume \\\\n=5\times 1=5\ moles[/tex]
Molecular mass of NaOH , M.M = 58.44 g/mol .
Mass of 5 moles of NaOH :
[tex]m=5\times 58.44\ g\\\\m=292.2\ g[/tex]
Hence , this is the required solution .
How many moles of salt are in 1.005 kg of NaCl? (Hint: 1 kg = 1000g)
O 17.8 mol
18.0 mol
17.2 mol
O 18.2 mol
Answer:
The answer is
17.2 molExplanation:
To find the number of moles in a substance when given the molar mass and mass we use the formula
[tex]n = \frac{m}{M } [/tex]
where
n is the number of moles
M is the molar mass
m is the mass of the substance
Mr( Na) = 23 , Mr( CL ) = 35.5
Molar mass ( NaCl ) = 23 + 35.5
= 58.5 g/mol
Mass = 1.005 kg
It's equivalent in grams is
1.005 × 1000 = 1005 g NaCl
So the number of moles in NaCl is
[tex]n = \frac{1005}{58.5} \\ = 17.179487...[/tex]
We have the final answer as
17.2 mol to the nearest tenth
Hope this helps you
Which statement below regarding evaporation is not correct?A. When a liquid is first placed in a closed container, the evaporation rate is higher than it is in an open container under the same conditions. B. When a liquid is first placed in a closed container, the evaporation rate is higher than the condensation rate. C. When the rates of evaporation and condensation are equal, the system has reached dynamic equilibrium. D. Vapor pressure refers to the pressure of a gas at a given temperature in equilibrium with its liquid phase. E. Stronger intermolecular forces within the liquid typically result in a lower vapor pressure under a given set of conditions.
Answer:
A. When a liquid is first placed in a closed container, the evaporation rate is higher than it is in an open container under the same conditions.
Explanation:
Evaporation refers to the process by which a liquid changes to gas or vapor. It usually occurs at the surface of a liquid.
Factors that affects evaporation include; nature of the liquid, surface area of liquid exposed, temperature and wind.
Considering the options given:
A. When a liquid is first placed in a closed container, the evaporation rate is higher than it is in an open container under the same conditions. = False
This is false because, the more the surface of the liquid exposed, the higher the rate of evaporation.
B. When a liquid is first placed in a closed container, the evaporation rate is higher than the condensation rate. = True
This is true because when a liquid is first placed in a container, the equilibrium position favors evaporation initially than condensation as saturation of the space above the liquid with vapor has not been achieved.
C. When the rates of evaporation and condensation are equal, the system has reached dynamic equilibrium.= True
Dynamic equilibrium is achieved when the rate of forward and backward reaction, in this case, evaporation and condensation are equal.
D. Vapor pressure refers to the pressure of a gas at a given temperature in equilibrium with its liquid phase. = True
E. Stronger intermolecular forces within the liquid typically result in a lower vapor pressure under a given set of conditions. = True
Strong intermolecular forces between the molecules of the liquid causes the liquid to remain in the liquid state rather than turning to vapor, thereby lowering vapor pressure
•What was the physical property used by mendeleev
in creating his periodio table?
Answer!
Answer:
Explanation: Mendeleev arranged the elements on the basis of their atomic mass. Melting and boiling point were used as the physical characteristics in deciding the position of elements. He arranged the elements and wrote the formula of their oxides and hydrides which seemed to possess same chemical formula.
Explanation:
7. Change the following data into scientific notation:
a. The distance between Pluto and the Sun is 5,913,000 km.
b. The density of nitrogen gas is 0.0012506 g/cm3.
Explanation:
A number can be written in the form of scientific notation as follows :
[tex]N=x\times 10^y[/tex]
x is any real number and y is integer
(a) The distance between Pluto and the Sun is 5,913,000 km.
There are 6 digits after 5. In scientific form is given by :
[tex]N=5.91\times 10^6\ km[/tex]
(b) The density of nitrogen gas is 0.0012506 g/cm³.
There are 2 digits before 1. In scientific notation,
[tex]d=1.25\times 10^{-3}\ g/cm^3[/tex]
A medical research lab in Europe is studying a drug’s absorption in the blood. Another lab in Japan is trying to delay the elimination of this drug from the blood so that it can act in the body for a longer period of time.
Based on this information, it can be concluded that scientific knowledge progresses due to the efforts of scientists
from different social and ethnic backgrounds.
from the most prestigious universities of the world.
who possess a high degree of efficiency.
who possess a high degree of skepticism.
The correct answer is From different social and ethnic backgrounds.
Explanation:
The purpose of science studies is to gain an understanding of specific phenomena and use this in the benefit of the world or humanity. Moreover, science is guided by objective methods and these are applied all around the world. This feature allows scientists from all kinds of social and ethnic backgrounds to study the same phenomena and obtain similar results, which is essential for the progress of scientific knowledge. This is exemplified by two different labs in two different countries studying drug absorption because the results of these two studies can be analyzed together to understand drug absorption.
In this context, one factor that contributes to the progress of scientific knowledge is the effort of scientists "from different social and ethnic backgrounds".
Answer:
The correct answer is From different social and ethnic backgrounds.
Explanation:
right on EDGE 2021
what is considered to be a physical property of matter
Answer: Some examples are color, density, volume and mass
Explanation:
Physical properties are anything you can smell, touch, or hear. They can be observed without changing.
CC14
Element
Compound
Which one is it
Draw the structure of 4-methyl-5-oxohexanal.
Answer:
Explanation:
The structural formula provides more information which is often used to represent a particular organic substance. A structural formula indicates how the atoms are arranged within the molecule of a substance. From the information, the structure of 4-methyl-5-oxohexanal is represented by using a stick formula where the methyl group falls into position 4 and oxygen group falls into position 5 on the hexanal compound.
The structure is provided in the image attached below for better understanding.
How many moles are there in 45.0 g of SF6?
Answer:
0.31 mole
Explanation:
The following data were obtained from the question:
Mass of SF6 = 45.0 g
Number of mole of SF6 =..?
Next, we shall determine the molar mass of SF6.
This can be obtained as follow:
Molar mass of SF6 = 32 + (19×6)
Molar mass of SF6 = 32 + 114
Molar mass of SF6 = 146 g/mol
Finally, we shall determine the number of mole in 45 g of SF6 as follow:
Molar mass of SF6 = 146 g/mol
Mass of SF6 = 45.0 g
Number of mole of SF6 =..?
Number of mole = mass /Molar mass
Number of mole of SF6 = 45 /146
Number of mole of SF6 = 0.31 mol
Therefore, 0.31 mol is present in 45 g of SF6.
Why is copper easier to produce than iron metal?A. Copper is easier to reduce than iron.B. Copper can be reduced by oxidizing the attached sulfur with oxygen. C. Iron requires toxic carbon monoxide for the reduction process. D. All of these are true.
Answer:
All of these are true.
Explanation:
Copper lies below iron in the activity series, this implies that copper is more easily reduced than iron as its electrode potential is positive.
Also, copper is extracted easily from its sulphide ore by oxidation with oxygen. Similarly, the reduction of iron in a blast furnace requires toxic CO, hence the answer above.
7. Why is the d-block one energy level behind the s-block? Also, why would the f-block be so far behind?
Answer:
7. Why is the d-block one energy level behind the s-block? Also, why would the f-block be so far behind?
me to
Explanation:
Definition of the word derived?
Answer:
obtain something from (a specified source).
Explanation:
Answer:
It is like the orgins of something
Which is a representation of a compound that gives the number of atoms and types of atoms in that compound?
What are the derived SI units?
Find the density of a sample that has a volume of 36.5L and a mass of 10.0kg
≈ 0,27 g/cm³
Explanation:36.5 l = 36.5 dm³ = 36500 cm³
10 kg = 10000 g
d = m/V
= 10000g/36500cm³
≈ 0,27 g/cm³
.
What volume of 10M NaOH would you need to add to a vessel, if your final
solution is 200 mL of 0.1M NaOH?
Answer:
2 mL
Explanation:
Step 1: Given data
Initial concentration (C₁): 10 MInitial volume (V₁): ?Final concentration (C₂): 0.1 MFinal volume (V₂): 200 mLStep 2: Calculate the volume of the 10 M solution
We want to prepare a diluted solution from a concentrated one. we can calculate the volume of the initial solution using the dilution rule.
C₁ × V₁ = C₂ × V₂
V₁ = C₂ × V₂/C₁
V₁ = 0.1 M × 200 mL/10 M
V₁ = 2 mL
Philip measures a room using his feet. (His feet are each about a foot long.) He estimates the room measures about ten and a half feet by thirteen and a half feet. He calculates the room’s area to be: 10.5’ × 13.5’ = 141.75 ft2.
Answer:
142 ft² (Approx)
Given:
Use feet as measurement device( Approx a foot long)
10.5’ × 13.5’ = 141.75 ft²
Find:
Best area for room
Explanation:
We know that Philip uses his feet to measures the area of the room which is not a proper unit of measurement, so we will take Philip's measurement to the maximum absolute unit
So,
Area of the room = 142 ft² (Approx)
When 3.0 kg of water is warmed from 10 °C to 80 °C, how much heat energy is needed?
Answer:
THE HEAT NEEDED TO CHANGE 3KG OF WATER FROM 10 C TO 80 C IS 877.8kJ OR 877,800 J.
Explanation:
Mass = 3.0 kg = 3 * 1000 = 3000 g
Initial temperature = 10 C
Final temperature = 80 C
Change in temperature = 80 - 10 = 70 C
Specific heat of water = 4.18 J/g C
Heat needed = unknown
Heat is the amount of energy in joules needed to change a gram of water by 1 C.
Heat = mass * specific heat * change in temperature
Heat = 3000 g * 4.18 J/g C * 70 C
Heat = 877 800 Joules
Heat = 877.8 kJ.
The heat needed to change 3 kg mass of water from 10 C to 80 C is 877,800 J or 877.8 kJ.
An atom has 14 protons, 16 neutrons, and 14 electrons. What is its mass number?
The answer is 30.
Explanation:
The total number of protons and neutrons in a nucleus is called mass number. So 14 proton plus 16 neutron is = 30 mass number.
For the following reaction, 2.45 grams of methane (CH4) are allowed to react with 27.7 grams of carbon tetrachloride . methane (CH4)(g) + carbon tetrachloride(g) dichloromethane (CH2Cl2)(g) What is the maximum mass of dichloromethane (CH2Cl2) that can be formed? grams What is the FORMULA for the limiting reagent? What mass of the excess reagent remains after the reaction is complete? grams
Answer:
The limiting reactant is CH₄
26.0g of CH₂Cl₂ is the maximum amount that can be formed
4.15g CCl₄ will remain
Explanation:
The reaction of methane, CH₄, with carbon tetrachloride, CCl₄ is:
CH₄ + CCl₄ → 2CH₂Cl₂
To find the maximum mass of dichloromethane that can be determined we need to find moles of methane and carbon tetrachloride:
Moles CH₄:
2.45g * (1mol / 16.04g) = 0.153 moles
Moles CCl₄:
27.7g * (1mol / 153.82g) = 0.180 moles
That means just 0.153 moles of CCl₄ will react until CH₄ is over.
The limiting reactant is CH₄
Assuming the whole 0.153 moles will react, the moles of CH₂Cl₂ will be:
0.153 moles CH₄ * (2 moles CH₂Cl₂ / 1 mole CH₄) = 0.306 moles of CH₂Cl₂
The mass is (Molar mass dichloromethane: 84.93g/mol):
0.306 moles of CH₂Cl₂ * (84.93g / mol) = 26.0g of CH₂Cl₂
The moles of CCl₄ that remain are:
0.180 moles - 0.153 moles = 0.027 moles
In grams:
0.027 moles * (153.82g / mol) = 4.15g CCl₄
Calculate the density of the following objects:
a. A box with a mass of 1500 grams that occupies 7600 mL of space.
Please help! will mark you as brainliesy
Answer:
Density =M/V
1500/7600
5.0666666667=Ans...
What is a Pure element ?
The concentration of dye in Solution A is 23.5 M. A serial dilution is performed to make Solutions B and C. In the first dilution, 2 mL of Solution A is diluted with 12 mL water to make Solution B. Then, 9 mL of Solution B is then diluted with 1 mL of water to make Solution C. What is the concentration of dye in Solution C? Provide your response to three significant figures in units of molarity.
Answer:
The concentration of dye in solution C is 3.02 M.
Explanation:
To find the concentration of dye in solution C we need to use the following equation:
[tex] V_{1}C_{1} = V_{2}C_{2} [/tex]
Where V is for volume and C is for concentration
In the first dilution we have:
[tex] V_{A}C_{A} = V_{T}C_{B} [/tex]
[tex] 2 mL*23.5 M = (2 mL + 12 mL)*C_{B} [/tex]
[tex] C_{B} = 3.36 M [/tex]
Now, in the second dilution:
[tex] V_{B}C_{B} = V_{T}C_{C} [/tex]
[tex] 9 mL*3.36 M = (9 mL + 1 mL)*C_{C} [/tex]
[tex] C_{C} = 3.02 M [/tex]
Therefore, the concentration of dye in solution C is 3.02 M.
I hope it helps you!
The combustion of palmitic acid is represented by the chemical equation: C16H32O2(s) + 23O2(g) → 16 CO2(g) + 16 H2O(l) The magnitude of ΔrU is ____________ in comparison to the magnitude of ΔrH a. The same b. Smaller c. Greater d. Need additional information
Answer:
The correct option is C
Explanation:
From the question we are told that
The reaction is
[tex]C_{16}H_{32}O_2(g) + 23O_2(g) \to 16 CO_2(g) + 16 H_2O(l)[/tex]
Generally [tex]\Delta H = \Delta U + \Delta N* RT[/tex]
Here [tex]\Delta H[/tex] is the change in enthalpy
[tex]\Delta U [/tex] is the change in the internal energy
[tex] \Delta N[/tex] is the difference between that number of moles of product and the number of moles of reactant
Looking at the reaction we can discover that the elements that was consumed and the element that was formed is [tex] O_2[/tex] and [tex]CO_2[/tex] and this are both gases so the change would occur in the number of moles
So
[tex]\Delta H = \Delta U + [16 -23]* RT[/tex]
[tex]\Delta H = \Delta U -7RT[/tex]
The negative sign in the equation tell us that the enthalpy[tex]\Delta_r H[/tex] would be less than the Internal energy [tex]\Delta_r U[/tex]
