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
Learn more: https://brainly.com/question/10038290
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.
One way to represent a substance is with a chemical formula. In the formula CO2, what do the symbols Cand o refer to?
Answer:
C is for carbon and O is for oxygen
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.
What types of materials are better at absorbing energy from radiation?
Answer:
Explanation:
Materials are clothes and heavy rope
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
Which of these is the best definition of biotechnology??
A) The study of chemical processes in living things
B) the use and application of living things and science
C) the application of engineering principles to solve medical problems
D) the study of forces
Which option BEST explains how thermal equilibrium interacts with heat transfer between particles?
a
Thermal equilibrium stops the transfer of energy in just one direction when both objects reach the same temperature, but allows their particles to continue transferring that energy back and forth.
b
Thermal equilibrium always transfers energy from the hotter object to the colder one, and increases the energy and speed of moving particles in both objects as the temperature decreases.
c
Thermal equilibrium helps the transfer of energy between the particles of some materials better than others, but always stops the transfer of energy in materials like plastic and wood.
d
Thermal equilibrium quickly transfers energy back to the particles of the object that was originally hotter, and requires that the particles in both objects have reached equal energy and density.
Answer:
Thermal equilibrium stops the transfer of energy in just one direction when both objects reach the same temperature, but allows their particles to continue transferring that energy back and forth.
Explanation:
a. The transfer of energy occurs until both objects reach thermal equilibrium. But particles are always moving and crashing with each other. TRUE.
b. The heat transfer occurs from the hotter object to the colder one but moving of particles descreases with temperature decreasing. FALSE.
c. Plastic and wood have a poor quality to transfer energy but there is no material that "stops" perfectly the transfer of energy. FALSE.
d. The heat is transferred from the particles of the hotter object to the particles of the colder one. FALSE
Which is an example of a current research focus in chemistry?
A. applying gene therapy to treat certain diseases
B. using hook-and-loop tape in the clothing industry
C. developing smoke detectors for common use
D. studying coal combustion as an energy source
Answer:
b is the correct answer
do not trust answer one
Explanation:
In which atmospheric layer is the ozone layer?
A.troposphere
B.mesosphere
C.stratosphere
D.thermosphere
Answer:
stratosphere
Explanation:
contains a high concentration of ozone in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere.
Answer:
stratosphere
Explanation: Most atmospheric ozone is concentrated in a layer in the stratosphere, about 9 to 18 miles (15 to 30 km) above the Earth's surface. Ozone is a molecule that contains three oxygen atoms.
In chemistry, one often uses a unit of charge known as the Faraday, F, which has the magnitude of the charge of 1 mole of electrons. How many faradays of charge does that correspond to
Answer:
1 Faraday
Explanation:
This question seeks to test proper understanding of Faraday's second law of electrolysis which states when the same quantity electricity passes through a solution of different electrolytes, the mass of the substance deposited is directly proportional to there chemical equivalence.
This law hints at the charges of ions being the chemical equivalence and also been represented as the unit for the quantity of electricity in faraday, F. Hence, a metal with the charge of 1+ can be displaced by 1F (which is equal to 96, 500 coloumbs). This charge also represents one molecule of electron, thus 1 faraday corresponds to one mole of electrons.
NOTE: It should be noted that a metal with the charge of 2+ can be displaced by 2F and so on.
If 25.6 mL isopropyl alcohol fully decomposes, what mass of H2 is formed? The density of isopropyl alcohol is 0.785 g/mL. g
Answer:
The correct answer is 0.67 g H₂
Explanation:
Isopropyl alcohol (C₃H₇OH) can decompose to give acetone (C₂H₆OH) and hydrogen gas (H₂) according to the following chemical equation:
C₃H₇OH (g) ⇒ C₂H₆CO(g) + H₂(g)
We can calculate the initial mass of isopropyl alcohol from the density and volume data:
density = m/V = 0.785 g/mL
⇒ m = density x V = 0.785 g/mL x 25.6 mL = 20.096 g C₃H₇OH
According to the chemical equation 1 mol of C₃H₇OH gives 1 mol H₂. The molar mass of C₃H₇OH is:
molar mass C₃H₇OH = (12 g/mol x 3) + (1 g/mol x 7) + 16 g/mol + 1 g/mol = 60 g/mol
molar mass H₂ = 1 g/mol x 2 = 2 g/mol
So, we obtain: 2 g H₂ from 60 g C₃H₇OH. We multiply this stoichiometric ratio (2 g H₂/60 g C₃H₇OH) by the initial mass of C₃H₇OH to obtain the mass of H₂ is formed:
20.096 g C₃H₇OH x (2 g H₂/60 g C₃H₇OH) = 0.6698 g ≅ 0.67 g H₂
A chemist decomposes samples of several compounds; the masses of their constituent elements are listed. Calculate the empirical formula for each compound.
a. 1.245 g Ni, 5.381 g I,
b. 2.677 g Ba, 3.115 g Br,
c. 2.128 g Be, 7.557 g S, 15.107 g
Answer:
you can see the empirical formula at the pic
The empirical formula for compound (a) is NiI2, (b) is BaBr2 and (c) is BeS.
What is empirical formula?
Empirical formula of a compound is defined as the simplest whole number ratio of atoms present in a compound.
(a) 1.245 g Ni : 5.381 g I
Mole of Ni ; Mole of I = 1.245/59 : 5.381/127 = 0.02 : 0.04 = 1:2
So the formula is NiI2
(b) 2.677 g Ba : 3.115 g Br
Mole of Ba : Mole of Br = 2.677/137 : 3.115/60 = 0.019 : 0.038
= 0.02 : 0.04 = 1:2
So the formula is BaBr2
(c) 2.128 g Be : 7.557 g S
Mole of Be : Mole of S = 2.128/9 : 7.557/32 = 0.2 : 0.2 = 1:1
So the formula is BeS
Thus, empirical formula for compound (a) is NiI2, (b) is BaBr2 and (c) is BeS.
To learn more about empirical formula, refer to the link below:
https://brainly.com/question/11588623
#SPJ2
for the following reaction, provide the missing information
Answer:
19. Option B. ⁰₋₁B
20. Option D. ²¹⁰₈₄Po
Explanation:
19. ²²⁸₈₈Ra —> ²²⁸₈₉Ac + ʸₓZ
Thus, we can determine ʸₓZ as follow:
228 = 228 + y
Collect like terms
228 – 228 = y
y = 0
88 = 89 + x
Collect like terms
88 – 89 = x
x = –1
Thus,
ʸ ₓZ => ⁰₋₁Z => ⁰₋₁B
²²⁸₈₈Ra —> ²²⁸₈₉Ac + ʸₓZ
²²⁸₈₈Ra —> ²²⁸₈₉Ac + ⁰₋₁B
20. ᵘᵥX —> ²⁰⁶₈₂Pb + ⁴₂He
Thus, we can determine ᵘᵥX as follow:
u = 206 + 4
u = 210
v = 82 + 2
v = 84
Thus,
ᵘᵥX => ²¹⁰₈₄X => ²¹⁰₈₄Po
ᵘᵥX —> ²⁰⁶₈₂Pb + ⁴₂He
²¹⁰₈₄Po —> ²⁰⁶₈₂Pb + ⁴₂He
Which number represetns a coefficient?
2
3
4
7
If your hypothesis is incorrect you should...
Which of the following is an Elementary compound?
A. CO2
B. N2
C. SO2
D. H2S
heeeeeeeeeelp please please please
Answer:
Explanation:
In my opinion the answer should be SO2
Answer:
a should be answer i think.
What is the Kc equilibrium-constant expression for the following equilibrium? S8(s) + 24F2(g) 8SF6(g)
Answer:
[tex]Kc=\frac{[SF_6]^8}{[F_2]^2^4}[/tex]
Explanation:
Hello.
In this case, for the undergoing chemical reaction:
[tex]S_8(s) + 24F_2(g) \rightleftharpoons 8SF_6(g)[/tex]
We consider the law of mass action in order to write the equilibrium expression yet we do not include S8 as it is solid and make sure we power each gaseous species to its corresponding stoichiometric coeffient (24 for F2 and 8 for SF6), thus we obtain:
[tex]Kc=\frac{[SF_6]^8}{[F_2]^2^4}[/tex]
Best regards!
When does carbon dioxide absorb the most heat energy?
during freezing
during deposition
during sublimation
during condensation
Answer:
during sublimation
Explanation:
just took the test
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.
A sample of propane, C3H8, contains 13.8 moles of carbon atoms. How many total moles of atoms does the sample contain
Answer:
[tex]Total = 50.6\ moles[/tex]
Explanation:
Given
[tex]Propane = C_3H_8[/tex]
Represent Carbon with C and Hydrogen with H
[tex]C = 13.8[/tex]
Required
Determine the total moles
First, we need to represent propane as a ratio
[tex]C_3H_8[/tex] implies
[tex]C:H = 3:8[/tex]
So, we're to first solve for H when [tex]C = 13.8[/tex]
Substitute 13.8 for C
[tex]13.8 : H = 3 : 8[/tex]
Convert to fraction
[tex]\frac{13.8}{H} = \frac{3}{8}[/tex]
Cross Multiply
[tex]3 * H = 13.8 * 8[/tex]
[tex]3 H = 110.4[/tex]
Solve for H
[tex]H = 110.4/3[/tex]
[tex]H = 36.8[/tex]
So, when
[tex]C = 13.8[/tex]
[tex]H = 36.8[/tex]
[tex]Total = C + H[/tex]
[tex]Total = 13.8 + 36.8[/tex]
[tex]Total = 50.6\ moles[/tex]
The empirical formula of CBr2 has a molar mass of 515.46 g/mol. What is the molecular formula of this
compound
Answer:
C3Br6
Explanation:
C= (1 X 12.011) = 12.011
Br= (2 X 79.904)= 159.808
159.808+12.011 = 171.819
515.46 divided by 171.819 = 3.00
so you mulitpy CBr2 by 3 which gives you C3Br6
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
When 435 J of heat is added to 3.4 g of olive oil that's at 21 Deg C, it's
temperature increases to 85 Deg C. Calculate the specific heat of Olive oil? Show work
Answer:
k Nishant
Explanation:
i don't know sorry but u can search in google
Is air a homogeneous heterogeneous mixture or substance
Answer:
look at the explanation
Explanation:
The air that you breathe is a homogeneous mixture of oxygen, nitrogen, argon, and carbon dioxide, along with other elements in smaller amounts. Because each layer of the Earth's atmosphere has a different density, each layer of air is its own homogeneous mixture.
Hope this helps. :)
calculate the mass of N2 gas which has a volume 0.227 at STP
How to separate given mixture?
Answer:
Chromatography involves solvent separation on a solid medium.
Distillation takes advantage of differences in boiling points.
Evaporation removes a liquid from a solution to leave a solid material.
Filtration separates solids of different sizes.
Explanation:
If 5.00g of iron metal is reacted with 0.950g of Cl2 gas, how many grams of ferric chloride (FeCl3) will form?
Answer:
1.45g of FeCl3
Explanation:
The equation of the reaction is given as;
2Fe + 3Cl2 --> 2FeCl3
2 mol of Fe reracts with 3 mol of Cl2 to form 2 mol of FeCl3
Upon converting to mass using;
Mass = Number of moles * Molar mass
( 2 * 55.85 = 111.7g ) of Fe reacts with ( 3 * 71 = 213g ) of Cl2 to form ( 2 * 162.2 = 324.4g) of FeCl3
Cl2 is the limiting reactant as it determines how much of FeCl3 is formed
213g of Cl2 = 324.4g of FeCl3
0.950g of Cl2 = x
x = (0.950 * 324.4 ) / 213
x = 1.45g of FeCl3
How do the test variables (independent variables) and outcome variables (dependent variables) in an experiment compare? A. The test variables (independent variables) and outcome variables (dependent variables) are the same things. B. The test variable (independent variable) controls the outcome variable (dependent variable). C. The test variable (independent variable) and outcome variable (dependent variable) have no affect on each other. D. The outcome variable (dependent variable) controls the test variable (independent variable).
Answer:
I'm on the exact same queston
Answer:
The test variable (independent variable) controls the outcome variable (dependent variable)
Explanation:
its right on study island
PLSSS HELP Match each image to the
correct step of meiosis. PLS HELP
Answer:
Explanation:
Here you go!! Hope this helps.
what’s the most abundant isotope of lawrencium
Answer:
266Lr
Thirteen isotopes of lawrencium are currently known; the most stable is 266Lr with a half-life of 11 hours, but the shorter-lived 260Lr (half-life 2.7 minutes) is most commonly used in chemistry because it can be produced on a larger scale.
Explanation:
hopefully that helps you
Define waves in your own words.
Answer:
Waves is the disturbance or variation that transfer energy from one location to other
Answer:
this is not in my words but i think this will help
(put some of the words you would use in this)
Explanation:
Transverse waves are always characterized by particle motion being perpendicular to wave motion. A longitudinal wave is a wave in which particles of the medium move in a direction parallel to the direction that the wave moves. ... Longitudinal waves are always characterized by particle motion being parallel to wave motion.
hope i helped