Answer:
Explanation:
Caffeine is a weak base with pKb = 10.4
Kb = 10⁻¹⁰°⁴ = 3.98 x 10⁻¹¹
molecular weight of caffeine = 194.2
455 x 10⁻³ g / L = 455 x 10⁻³ / 194.2 moles / L
concentration of given solution a = 2.343 x 10⁻³ M
Let the caffeine be represented by B .
B + H₂O = BH + OH⁻
a - x x x
x² / ( a - x ) = Kb
x² / ( a - x ) = 3.98 x 10⁻¹¹
x is far less than a so a -x is almost equal to a
x² = 3.98 x 10⁻¹¹ x 2.343 x 10⁻³ = 9.32 x 10⁻¹⁴
x = 3.05 x 10⁻⁷
[ OH⁻ ] = 3.05 x 10⁻⁷
pOH = - log ( 3.05 x 10⁻⁷ )
= 7 - log 3.05
= 7 - 0.484 = 6.5
pH = 14 - 6.5 = 7.5
The pH of 455 mg/L of caffeine is 7.5
Using the formula;
Mass concentration = molar concentration × molar mass
Molar mass of caffeine = 194 g/mol
Mass concentration of caffeine = 455 mg/L
Molar concentration = Mass concentration/molar mass
Molar concentration = 455 × 10^-3g/L/194 g/mol
= 0.00235 M
Let Caffeine by depicted by the general formula BH
We can now set up the ICE table as follows;
:B + H2O ⇄ BH + OH^-
I 0.00235 0 0
C - x +x +x
E 0.00235 - x x x
Note that water is present in large excess
Again; pKb of caffeine =10.4
Kb = Antilog[-pKb]
Kb = Antilog [-10.4]
Kb = 3.98 × 10^-11
Kb = [BH] [OH^-]/[:B]
3.98 × 10^-11 = [x] [x]/[ 0.00235 - x ]
3.98 × 10^-11 [ 0.00235 - x ] = [x] [x]
9.4 × 10^-14 - 3.98 × 10^-11x = x^2
x^2 + 3.98 × 10^-11x - 9.4 × 10^-14 = 0
x = 3.1 × 10^-7 M
Recall [BH] = [OH^-] = 3.1 × 10^-7 M
Now;
pOH = - log [OH^-]
pOH = log [3.1 × 10^-7 M]
pOH = 6.5
But;
pH + pOH = 14
pH = 14 - pOH
pH = 14 - 6.5
pH = 7.5
The pH of 455 mg/L of caffeine is 7.5
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Missing parts
Caffeine (C8H10N4O2) is a weak base with a pKb of 10.4. Calculate the pH of a solution containing a caffeine concentration of 455 mg/L.
Cementation is part of the process of
A. igneous intrusion
B. lithification
C. igneous extrusion
D. metamorphism
SUBMIT
Answer:
The correct answer is b.
Explanation:
hope this helps u
Answer:
Bryna is correct it is B
Explanation:
Please help. The question is in the picture
How many grams of sodium hypochlorite (NaClO)is required to make abuffer with pH= 7.35 if you had 500 mL of a 0.1M solution of hypochlorous acid with pKa=7.54.(Assume the addition of NaClO does not change the volume.)
Answer:
2.4g of NaClO must be added
Explanation:
To find the pH of a buffer we must use H-H equation:
pH = pKa + log [A⁻] / [HA]
Where pH is the pH of the buffer, 7.35
pKa of the HClO buffer is 7.54
[A⁻] could be taken as moles of NaClO
And [HA] moles of the weak acid: 500mL = 0.500L * (0.1mol/L) = 0.05 moles
Replacing:
pH = pKa + log [A⁻] / [HA]
7.35 = 7.54 + log [A⁻] / [0.05moles]
0.6457 = [A⁻] / [0.05moles]
0.03228 moles = Moles of NaClO we need to make the pH = 7.35 buffer.
To convert these moles to grams we use the molar mass of NaClO (74.44g/mol):
0.03228 moles * (74.44g/mol) =
2.4g of NaClO must be added
A compound containing only carbon, hydrogen, and oxygen is analyzed using combustion analysis. When 50.1 g of the compound is burned, 91.8 g of carbon dioxide and 25.1 g of water are collected. In order to determine the moles of carbon in the compound, first determine the moles of carbon dioxide that were produced from the combustion.
Answer:
[tex]C_{3}H_4O_2[/tex]
Explanation:
Hello,
In this case, since the carbon of the initial compound is present in the carbon dioxide product, we can compute the mass and moles of carbon in the compound:
[tex]n_C=91.8g CO_2*\frac{1molCO_2}{44gCO_2} *\frac{1molC}{1molCO_2} =2.09molC\\\\m_C=91.8g CO_2*\frac{1molCO_2}{44gCO_2} *\frac{1molC}{1molCO_2}*\frac{12gC}{1molC} =25.0gC[/tex]
Next, the mass and moles of hydrogen in the compound, is contained in the yielded amount of water, thus, we compute the mass and moles of hydrogen in the compound:
[tex]n_H=25.1gH_2O*\frac{1molH_2O}{18gH_2O} *\frac{2molH}{1molH_2O} =2.79molH\\\\m_H=25.1gH_2O*\frac{1molH_2O}{18gH_2O} *\frac{2molH}{1molH_2O} *\frac{1gH}{1molH} =2.79gH[/tex]
In such a way, the mass of oxygen comes from the mass of the compound minus the mass of carbon and oxygen:
[tex]m_O=50.1g-25.0g-2.79g=22.31gO[/tex]
And the moles:
[tex]n_O=22.31gO*\frac{1molO}{16gO}=1.39molO[/tex]
Then, we compute the subscripts by diving the moles of C, H and O by the moles of oxygen as the smallest moles:
[tex]C:\frac{2.09}{1.39}=1.5 \\\\H:\frac{2.79}{1.39}=2\\ \\O:\frac{1.39}{1.39} =1[/tex]
After that, we write:
[tex]C_{1.5}H_2O[/tex]
Which must be shown in whole number only, thereby we multiply the subscripts by 2, so the empirical formula turns out:
[tex]C_{3}H_4O_2[/tex]
Best regards.
True or False: The exact location of an electron can be measured thanks to
modern science.
Answer:
false you can not get a exact location of electrons from just modern science
Label the parts of the electric circuit that best correspond to the heart, arteries, veins, and cells.
Answer:
1 ➡️ Cells
2 ➡️ Arteries
3 ➡️ Veins
4 ➡️ Heart
Explanation:
The parts of the electric circuit that best correspond to the heart, arteries, veins, and cells have been properly labeled.
The circulatory system involves the transportation of nutrients, oxygen and water by blood to other the parts of the body.
From the electric circuit, we see that arteries transport blood away from the heart to the other cells in the body. The veins actually return the blood back to the heart from the cells. The heart pumps the blood
The electric circuity diagram has the label 1 bulb analogous to cell, label 2 analogous to arteries, label 3 analogous to veins, and label 4 cell analogous to heart.
What is an electric circuit?The electric circuit has been given as the power source and the conducting wires that allows the flow of the current in the circuit.
In the human body, the heart has been transported the oxygenated blood through the arteries to the cell and carried the deoxygenated blood from the cells back to the heart via veins.
In the circuit, the battery has been the source of the power/blood. The current has been carried from the heart to the cell/bulb through the arteries labeled, 2, and transported back to the battery via veins labeled 3.
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Each molecule of an olefin has at least:
a
one double bond
b
two double bonds
c
three double bonds
d
two or more single bonds
Answer:
a.
Explanation:
One double bond.
For example ethene CH2=CH2
What type of energy is defined as the kinetic energy of the atoms of a substance?
Explanation:Thermal energy, or heat, is the energy that comes from the movement of atoms and molecules in a substance. Heat increases when these particles move faster. Geothermal energy is the thermal energy in the earth. Motion energy is energy stored in the movement of objects.
I hope this helped!
PLEASE HELP!!!!! CHEMISTRY
What is the formula for Maganese (IV) Oxalate ?
Answer:C2MnO4
You can get this by looking at your periodic table :)
What characteristics are used to clarify an area as a wetland?
what isotope of an atom if it has 29 protons and 36 neutrons
Answer:
POTASSIUM
Explanation:
2 8 8 1________ 1A
Naphthalene is soluble in diethyl ether, but it is insoluble in water regardless of the solution pH. Explain why this compound cannot be readily ionized in aqueous solution.
Answer:
Naphthalene is a non polar substance
Explanation:
In chemistry, the principle of like dissolves like is the over aching principle that controls the dissolution of one substance in another.
Naphthalene dissolves in diethyl ether because diethyl ether is a non polar solvent just as naphthalene is a nonpolar substance.
Since water is a polar solvent, it can not dissolves naphthalene at any pH because naphthalene is a nonpolar substance.
As the space in a container gets smaller, the _____
decreases.
O A) pressure
O B) temperature
O c) volume
O D) heat
Answer:
A
Explanation:
As the space in a container gets, smaller the volume decreases because volume is a measure of the space that the particles can occupies inside.
What is volume?Volume is the space occupied by a substance and which is directly proportional to temperature according to Boyles law and inversely proportional to the pressure.
As the temperature increases, volume increases whereas the pressure increases, volume get decreased. As there are more particles but the space inside a container is small, then their volume is said to be smaller.
Hence, option C is the answer.
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#SPJ5
How does the motion of particles in the sun’s plasma compare to the motion of particles in a solid?
Particles in both the plasma and a solid move around to fill available space.
Particles in the plasma move randomly, but particles in a solid vibrate in one place.
Particles in the plasma have low kinetic energy, but particles in a solid have high kinetic energy.
Particles in both the plasma and a solid are made up of fast-moving electrons and cations.
Answer:
Particles in the plasma move randomly, but particles in a solid vibrate in one place.
Explanation:
how do you find protons in an atom?
Answer:
Protons are always found in the nucleus of an atom.
Explanation:
Protons and neutrons make up the nucleus of an atom, which is in the center. The electrons "orbit" the nucleus.
Answer:
The number of protons, neutrons, and electrons in an atom can be determined from a set of simple rules.
Explanation:
The number of protons in the nucleus of the atom is equal to the atomic number (z). The number of electrons in a neutral atom is equal to the number of protons.
What is an advantage of making plant-based products, such as cotton, instead of making petroleum-based products, such as plastics?
A Producing plant-based products requires more energy.
B Factories that make plant-based products generate more waste.
C Plants that are used to make the product can be replaced.
D All plant-based products cost more than petroleum-based products.
Answer:
Hey! sorry if im late but the
answer is :
C : Plants that are used to make the product can be replaced.
I hope this helps everyone out there!
Explanation:
i guessed lol
Answer:
C) Plants that are used to make the product can be replaced
Explanation:
Sorry I’m late I just did the test and got 100%
Plz answer me will mark as brainliest
Answer:
Compared to the walls of the right ventricle, the walls of the left ventricles are much thicker.
The plasma carries hormones, which are the body's chemical messengers.
NEED HELP ASAP !
Which best describes an element?
A. elements are chemicals that are pure substance held together by chemical bonds
B. elements are mixtures of protons, neutrons, and electrons in different combination
C. elements are chemicals that are pure substances represented by symbols that have at least one capital letter
D. elements that are chemicals that are formed when temperature change happens or a precipitate forms
Answer:
A. Elements are pure substances.
Explanation:
Out of all four answers A would be best. Hope this helps.
Answer:
B
Explanation:
I think all options can define element in one form or another but an element is characterized by the atomic number it has i.e you will know it's Carbon due to it's number of protons, neutrons and/or electrons.
In what ways are physical and chemical weathering alike? In what ways are they different?
A tree frog uses plants or trees for protection from the rain. The frog is protected from the rain and the tree is neither helped nor harmed
Describe the Bay's salinity. How does the salinity change throughout the year?
Which of the following does Electrons change when Electrons are changed?
Answer:
tuttutututu and the optionsWhich Drug is used not to cure Cancer, but can kill Cancer?
(A) = Adrenaline.
(B) = Burger King.
(C) = Chemotherapy.
(D) = Deoxyribose.
(E) = Ethanol.
Answer:
chemotherapy
Explanation:
Pb12 (s) = Pb+2 (aq)
+
2 ]- (aq)
Answer:
this
Explanation:
What is the unit rate of the better deal? (Number answers only.)
LaTeX: \frac{160\:miles}{5\:gallons}\:or\:\frac{315\:miles}{9\:gallons}160 m i l e s 5 g a l l o n s o r 315 m i l e s 9 g a l l o n s
The better deal has a unit rate of [m] miles per gallon.
According to Avogadro's law, what is characteristic of 1 mole of gas at STP?
A. It occupies 22.4 L.
B. It occupies no volume.
C. It occupies 1 L.
D. It will expand to any volume.
Answer:
A. It occupies 22.4 L
Explanation:
STP (Standard Conditions for Temperature and Pressure) = 22.4 L per mole at 1 atm
Avogadro's Law states that 1 mol at 1 atm occupies 22.4 L.
8. Besides landforms, the other large features that cover the
surface of the earth are ______.
A. islands
B. waterways
C. deserts
D. lakes
Answer:
A landform is a feature on the Earth's surface that is part of the terrain. Mountains, hills, plateaus, and plains are the four major types of landforms. Minor landforms include buttes, canyons, valleys, and basins. Tectonic plate movement under the Earth can create landforms by pushing up mountains and hills.
Explanation:
"Waterways" are the other large features that cover the surface of the earth.
Waterways
A canal would be any body of water throughout which boats may move. Waterways, on the other hand, comprise waterways that seem to be expansive as well as shallow enough already to allow freight-carrying watercraft just to travel through.
Some bodies of water are usually regularly dredged to maintain an appropriately deep course throughout all circumstances. Dams change the depth of other rivers in particular parts.
Thus the response above i.e., "Option B" is correct.
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What is the atomic mass of element X
Answer:
Which one of the table is element X?
Explanation:
I have no idea and help!!!!!!!!!!!!!!!!!!!!!!!!!
can someone pweaseee help me on this ??
Answer:
Be
Explanation:
The atomic radius decreases as you go from left to right in a period. Be has the largest radius out of those given elements.
You may have to recrystallize any or all of the components of your extraction mixture, benzoic acid, ethyl-4-aminobenzoate and fluorenone, depending on their purity after isolation. You should have the recystallization solvents in your protocol. They are respectively:
Answer:
the Recrystallization solvents are;
-Sodium Hydroxide Base (NaOH)
- Hydrochloric Acid (HCl)
- Sand bath when acidic and basic components are removed.
Explanation:
Recrystallization is simply a technique used to purify an impure compound in a solvent.
Now, we want to purify the mixture of benzoic acid, Ethyl-4-aminobenzoate and fluorenone.
For the benzoic acid, it can be separated out of the mixture by addition of sodium hydroxide base (NaOH).
The Ethyl - 4 - aminobenzoate will be separated from the mixture by the addition of Hydrochloric Acid (HCl).
The fluorenone would be separated out by heating the mixture in a sand bath after the basic and acidic components have already been extracted out.
Thus, the Recrystallization solvents are;
-Sodium Hydroxide Base (NaOH)
- Hydrochloric Acid (HCl)
- Sand bath when acidic and basic components are removed.
Which element is classified as a noble gas?
Answer:
The elements with completely filled shells are classified as noble gases
That is why we only see noble gases on the rightmost corner of the periodic table, it is because they have the maximum number of electrons in a shell
Examples of noble gases
Helium , Neon , Argon and Krypton are some examples of noble gases
Answer:
D. (Xe) XenonExplanation:
I JUST TOOK THE TEST!