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.
Electrolysis of water produces its constituent elements, hydrogen and oxygen. This process is represented by the following balanced chemical equation:
2 H2O(l) → 2 H2(g) + O2(g).
If 8.05 grams of oxygen gas was produced in the reaction, how many molecules of water were decomposed?
Do enter the coefficient of the answer only. Do NOT include the unit in final answer.
_______________________________ × 1023 H2O molecules.
Answer:
3.011 × 10²³
Explanation:
Given data:
Mass of oxygen produced = 8.05 g
Molecules of water decomposed = ?
Solution:
Balance chemical equation:
2H₂O → 2H₂ + O₂
Number of moles of oxygen produced:
Number of moles = mass/molar mass
Number of moles = 8.05 g/ 32 g/mol
Number of moles = 0.25 mol
Now we will compare the moles of water with oxygen.
O₂ : H₂O
1 : 2
0.25 : 2×0.25 =0.5 mol
0.5 moles of water were decomposed.
Molecules of water decomposed:
1 mole = 6.022× 10²³ molecules of water
0.5 mol ×6.022× 10²³ molecules of water/ 1mol
3.011 × 10²³ molecules of water
Conductivity is an example of what type of property?
Answer:
A physical property is a characteristic of matter that is not associated with a change in its chemical composition. Familiar examples of physical properties include density, color, hardness, melting and boiling points, and electrical conductivity.
Explanation:
Conductivity is an example of a physical property. Physical properties are characteristics of a substance that can be observed or measured without changing the substance's chemical composition.
Conductivity specifically refers to a material's ability to conduct electricity or heat. Materials with high electrical conductivity allow electricity to flow easily through them, while materials with high thermal conductivity conduct heat efficiently.
Examples of conductive materials include metals like copper and aluminium, which are widely used in electrical wiring and heat transfer applications due to their excellent conductivity properties.
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3 letters start from X
Answer:
xanthophyll
xenobiotic
xenon
X group
x-rays
x-ray tube
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.
How many of the 7 traits of living things have
Answer:
What do you mean by this?
Explanation:
The pOH of an aqueous solution of 0.480 M trimethylamine (a weak base with the formula (CH3)3N) is .
Answer:
Explanation:
Kb of (CH₃)₃N is 7.4 x 10⁻⁵
initial concentration of (CH₃)₃N a is .48 M
(CH₃)₃N + H₂O = (CH₃)₃NH⁺ + OH⁻
a - x x x
x² / (a - x ) = Kb
x is far less than a so a - x can be replaced by a .
x² / a = Kb
x² = a x Kb = .48 x 7.4 x 10⁻⁵ = 3.55 x 10⁻⁵ = 35.5 x 10⁻⁶
x = 5.96 x 10⁻³
pOH = - log ( 5.96 x 10⁻³ )
= 3 - log 5.96
= 3 - .775
= 2.225
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.
A rook is dropped into a graduated cylinder filled with 35 mL of water.
What is the volume of the rock? (Hint: 1 ml water = 1 cm?)
40 cm
O 14 cm
O 5 cm
O 35 cm
Answer:
5 cm³.
Explanation:
The following data were obtained from the question:
Volume of water = 35 mL
Volume of water + Rock = 40 mL
Volume of rock =.?
The volume of the rock can be obtained as follow:
Volume of rock = (Volume of water + Rock) – (Volume of water)
Volume of rock = 40 – 35
Volume of rock = 5 mL
Finally, we shall convert 5 mL to cm³. This can be obtained as illustrated below:
1 mL = 1 cm³
Therefore,
5 mL = 5 cm³
Thus, the volume of the rock is 5 cm³.
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.
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 the temperature of o3 gas if the average speed(actually the root mean square speed of the molecules is 750 m/s
Answer:
1.08 × 103 K
hope this helps :)
Explanation:
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.
Violet light has a wavelength of 4.50 x 10-12 m. What is the frequency?*
3 points
1.5 x10^20 1/s
0.0135 1/s
6.77x10^19 1/5
3x10^8 1/s
Green light has a frequency of 6.73 x 1014 1/s. What is the wavelength?*
3 points
2.24x10^6 m
4.46x10^-7 m
2.02 x 10^23 m.
4.95 x 10^-24 m
3 points
What is the energy (Joules) of violet light with a frequency = 3.43 x 10^14
1/s? *
4.54x10^-19 J
1.99x10^-25 J
1.93 x 10^-48 J
2.27 x 10^-19 J
Answer:
Frequency = 6.67x10¹⁹ s⁻¹
Wavelength = 4.46x10⁻⁷m
e = 2.27x10⁻¹⁹J
Explanation:
To convert frequency to wavelength and vice versa we use the equation:
Wavelength = Speed of light / Frequency
Speed ligth is 3x10⁸m/s
For a wavelength of 4.50x10⁻¹²m:
4.50x10⁻¹²m = 3x10⁸m/s / Frequency
Frequency = 3x10⁸m/s / 4.5x10⁻¹²m
Frequency = 6.67x10¹⁹ s⁻¹For a frequency of 6.73x10¹⁴s⁻¹:
Wavelength = 3x10⁸m/s / 6.73x10¹⁴s⁻¹
Wavelength = 4.46x10⁻⁷mAnd energy, e, from frequency, is obtained as follows:
e = h ₓ frequency
Where h is Planck's constant, 6.626x10⁻³⁴J*s
e = 6.626x10⁻³⁴J*s*3.43x10¹⁴s⁻¹
e = 2.27x10⁻¹⁹JThe heat of fusion for naphthalene is 0.148 kJ/g. Calculate the heat energy in joules required to melt 52.95 g of naphthalene.
Answer:
7836.6 J
Explanation:
The following data were obtained from the question:
Heat of fusion (Hf) = 0.148 KJ/g
Mass (m) = 52.95 g
Heat (Q) required =..?
The heat (Q) required to melt the sample of nephthalene can be obtained as follow:
Q = m·Hf
Q = 52.95 × 0.148
Q = 7.8366 KJ
Finally, we shall convert 7.8366 KJ to Joule (J) in order to obtain the desired result. This can be obtained as follow:
1 kJ = 1000 J
Therefore,
7.8366 KJ = 7.8366 KJ × 1000 J / 1 KJ
7.8366 KJ = 7836.6 J
Therefore, 7.8366 KJ is equivalent to 7836.6 J
Thus, 7836.6 J of heat energy is required to melt the sample of nephthalene.
The heat required for melting of 52.95 g of naphthalene has been 7.8366 kJ.
The heat of fusion has been the energy required by 1g for the change in the substance.
The heat required to melt naphthalene can be given as:
Heat = mass × Heat of fusion
The given mass = 52.95 g
The heat of fusion = 0.148 kJ/g
The heat required can be given as:
Heat = 0.148 × 52.95 kJ
Heat = 7.8366 kJ.
The heat required for melting of 52.95 g of naphthalene has been 7.8366 kJ.
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The specific heat of silver is 0.235 J/gx °C. How much heat is needed to raise the temperature of an 8-gram silver ring by 50°C
Answer:
Heat needed to increase the temperature by 50°C is 94 j.
Explanation:
Given data:
Specific heat of silver = 0.235 j/g.°C
Heat needed to increase temperature = ?
Mass of silver = 8 g
Temperature difference = ΔT= 50°C
Solution:
Formula:
q = mcΔT
c = specific heat capacity of substance
Now we will put the values i formula.
q = 8 g× 0.235 J/g.°C× 50°C
q = 94 J
Heat needed to increase the temperature by 50°C is 94 j.
Which of the following is true?
A) The closer an electron is to the nucleus, the higher its energy level.
B) The closer an electron is to the nucleus, the lower its energy level.
C) The closer an electron is to the nucleus, the more its energy level fluctuates.
D) There is no relationship between proximity to the nucleus and the energy level of an electron
Answer:
B) The closer an electron is to the nucleus the lower it's energy level.
Explanation:
This is because the attractive force for electrons to the nucleus is stronger. Thus, the orbital energy becomes less.
hello I am working on naming compounds and wondering if you could help me figure out the name
Al2(SO4)3 aluminium sulfate
The same ball is hit again and experiences a net force of 3.5 N instead. What is the acceleration of the volleyball?
Answer:
I hope this helped :)
Explanation:
a=f/m
a=3.5N/.25 kg
a=14m/s2
The acceleration of the volleyball is 14 m/s²
A force is defined to be a pull or a push acting on an object. The force exerted on an object can be said to be determined if the mass of the object is known.
It can be calculated by using the expression;
Force (F) = mass (m) × acceleration (a)
From the given information;
The net force acting on the ball after it hits again = 3.5 NLet assume that the mass of the ball is 0.25 kg since it is not given∴
The acceleration of the above expression can be computed as:
acceleration (a) = Force (F) / mass (a)
acceleration (a) = 3.5 / 0.25
acceleration (a) = 14 m/s²
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Consider the reaction of 30.0 mL of 0.235 M BaI₂ with 20.0 mL of 0.315 M Na₃PO₄.
Which of the following compounds would be the precipitate that forms?
a) Bal2
b) Na3PO4
c) Ba3(PO4)2
d)Nal
Answer:
C
Explanation:
Because sodium is basically always soluble with any compound, it is between a and c. a is part of the reactant so it cant be A. So C.
The statement, that describes the compounds would be the precipitate that forms in the reaction is "Ba3(PO4)2"
What is precipitate?Precipitate is a solid generated by a change in a solution, usually due to a chemical reaction or a change in temperature that reduces a solid's solubility.
What is compound?The combination of more than one element will be identified ad compound.
When cations and anions in aqueous solution combine to create an insoluble ionic solid called a precipitate, double displacement reactions occur, resulting in the formation of a solid form residue. Except for salts of Group 1 metals and ammonium, salts of phosphates and carbonates ions are insoluble, according to the solubility flow chart. The production of a solid white precipitate is used to demonstrate the insoluble nature of barium phosphate.
Hence the correct option is c.
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Which statement gives an advantage of multicellular organisms?
A. Cells are able to provide support
B. They can reproduce quickly
C. Their size allows them to maintain structure easily
D. They need small amounts of energy
Answer:
A. Cells are able to provide support
ppm is used to describe very small amounts of substance?
parts per million (ppm), parts per billion (ppb) and parts per trillion (ppt) are the most commonly used terms to describe very small amounts of substances. a ppm of a chemical in water means that, in a million units of water, there would only be one unit of the chemical.
During photosynthesis, plants and some other organisms use energy from the sun to convert (change): carbon dioxide (CO2) and water (H2O) into ____________ (O2) and __________ (C6H12O6)
Answer:
CO2 + H2O → O2 + C6H12O6
CO2 = carbon dioxide
H2O = water
O2 = oxygen
C6H12O6 = glukose
give reason deliquescent substance truns into liquid when exposed to atmosphere air
Which of the following correctly lists the five atoms in order of increasing size (smallest to
largest)?
O, F, Mg, S, Ba
Answer:
F - O - S - Mg - Ba
Explanation:
as you move left to right on the periodic table the number of electrons increase.
The correct lists of the five atoms in order of increasing size smallest to
largest is :
D) F - O - S - Mg - Ba
Atomic RadiusThe correct lists of the five atoms in order of increasing size smallest to
largest is F - O - S - Mg - Ba.
The atomic radius of a chemical element may be a degree of the measure of its molecule, as a rule the mean or commonplace remove from the center of the core to the furthest isolated electron.
The arrange will be:
Fluorine(F) (50 pm)Sulfur(S) (100 pm) Magnesium(Mg) (150 pm) Barium(Ba) (215 pm)As you move cleared out to right on the periodic table the number of electrons increment.
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what is the chimestry
Which of the three crowns was made of gold? Explain:
Answer:
I need more context. Maybe add a picture.
Explanation:
Answer:
Crown B
Explanation:
because the density of gold is 19.3 and the density of the crown is 19.29.
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 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 sample of an ideal gas has a volume of 2.23 L at 289 K and 1.05 atm. Calculate the pressure when the volume is 1.08 L and the temperature is 304 K. P= atm
Answer:
2.28 atm
Explanation:
V₁ = 2.33L, V₂ = 1.08L
T₁ = 289K, T₂ = 304K
P₁ = 1.05 atm, P₂ = ?
Where V₁ and V₂ are initial and final volume respectively
T₁ and T₂ are initial and final temperature respectively
P₁ and P₂ are initial and final pressure respectively
The formula to be used here is the general gas equation:
P₁V₁/T₁=P₂V₂/T₂
1.05 × 2.23/289 = P₂ × 1.08/304
P₂ × 1.08 × 289 = 1.05 × 2.23 × 304
P₂ = (1.05 × 2.23 ×304) ÷ (1.08 × 289)
P₂ = 711.82 ÷ 312.12
P₂ = 2.28 atm
Use the drop-down menu to complete the statement.
Atoms of elements in the same group have the same number of
. This is why they have similar chemical properties.
Answer:
valence electrons
Explanation:
other guy was close enough
Atoms of elements in the same group have the equal number of valence electrons. That is why they have similar chemical properties.
Why does the element in the same group have similar chemical behavior?The chemical properties of elements depend on the number of valence electrons in their outermost shell. Those elements which are placed in the same group in the periodic table have the same number of valence electrons.
Therefore, elements present in the same group of the modern periodic table have similar chemical behavior.
The elements having a similar valence shell electronic configuration in their atoms are arranged in the same group of the periodic table. These valence electrons decide the chemical properties and reactivities of the chemical elements.
For example, all the elements in group 1 of the periodic table have one electron in their valence shell and all the elements present in group 17 have seven electrons in their valence shell.
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