Answer:
75603.86473 K
Explanation:
Given that:
The 1st excited electronic energy level of He atom = 3.13 × 10⁻¹⁸ J
The objective of this question is to estimate the temperature at which the ratio of the population will be 5.0 between the first excited state to the ground state.
The formula for estimating the ratio of population in 1st excited state to the ground state can be computed as:
[tex]\dfrac{N_2}{N_1} = e ^{^{-\dfrac{(E_2-E_1)}{KT}}} = e ^{^{-\dfrac{(\Delta E)}{KT}}}[/tex]
From the above equation:
Δ E = energy difference = 3.13 × 10⁻¹⁸ J
k = Boltzmann constant = 1.38 × 10⁻²³ J/K
[tex]\dfrac{N_2}{N_1} = 0.5[/tex]
Thus:
[tex]0.05 =e^{^{ -\dfrac{3.13 \times 10^{-18} \ J}{1.38\times 10^{-23 \ J/K}\times T}}}[/tex]
[tex]In (0.05) = { -\dfrac{3.13 \times 10^{-18} \ J}{1.38\times 10^{-23 \ J/K}\times T}}}[/tex]
[tex]-3.00 = { -\dfrac{3.13 \times 10^{-18} \ J}{1.38\times 10^{-23 \ J/K}\times T}}}[/tex]
[tex]-3.00 = -226811.5942 \times \dfrac{1}{T}[/tex]
[tex]T = \dfrac{-226811.5942}{-3.00 }[/tex]
T = 75603.86473 K
The molarity (M) of an aqueous solution containing 22.5 g of sucrose (C12H22O11) in 35.5 mL of solution is ________.
Answer:
1.86 M
Explanation:
From the question given above, the following data were obtained:
Mass of sucrose (C12H22O11) = 22.5 g
Volume of solution = 35.5 mL
Molarity of solution =?
Next, we shall determine the number of mole in 22.5 g of sucrose (C12H22O11). This can be obtained as follow:
Mass of sucrose (C12H22O11) = 22.5 g
Molar mass of C12H22O11 = (12×12) + (22×1) + (16×11)
= 144 + 22 + 176
= 342 g/mol
Mole of C12H22O11 =?
Mole = mass /Molar mass
Mole of C12H22O11 = 22.5 /342
Mole of sucrose (C12H22O11) = 0.066 mole
Next, we shall convert 35.5 mL to litres (L). This can be obtained as follow:
1000 mL = 1 L
Therefore,
35.5 mL = 35.5 mL × 1 L / 1000 mL
35.5 mL = 0.0355 L
Thus, 35.5 mL is equivalent to 0.0355 L.
Finally, we shall determine the molarity of the solution as follow:
Mole of sucrose (C12H22O11) = 0.066 mole
Volume of solution = 0.0355 L.
Molarity of solution =?
Molarity = mole /Volume
Molarity of solution = 0.066/0.0355
Molarity of solution = 1.86 M
Therefore, the molarity of the solution is 1.86 M.
Explain why a buffer can be prepared from a mixture of NH4CL and NaOH but not from NH3 and NaOH .
A buffer solution is often referred to as a mixture of an aqueous solution of a weak acid and its conjugate base or weak base and its conjugate acid.
NH4CL is a weak base and NaOH is a strong base and when both it gives you a basic buffer and the result will give you an acid/base needed for the buffer.NH 3 is a weak base, but NaOH is a strong base and therefore the combination of these solutes would not make a buffer solution because both will give you a base and no acid.Conclusively we can say that an acid or base needed for making buffer solutions and not base alone
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A buffer solution of volume 0.500 L contains 1.68 g NH3and 4.05 g (NH4)2SO4.
Required:
a. What is the pH of this solution?
b. If 0.88 g of NaOH is added to the solution, what will be the pH?
Answer:
wait
Explanation:
a. The pH of this solution is 9.45.
b. If 0.88 g of NaOH is added to the solution, the pH will be 9.74.
What is pH means?a way to gauge how basic or acidic a material or solution is. On a scale of 0 to 14, pH is measured. A pH of 7 indicates neutrality on this scale, which implies it is neither acidic nor basic. More basic substances have a pH value more than 7, whereas more acidic substances have a pH value less than 7.
first of all we should calculate the molarity of the compounds
no. of moles of NH₃ = weight / molecular weight = 1.68 / (14+3) = 0.099
no. of moles of (NH₄)2SO4 = 4.05 / {2×(14+4) + 32 + 64} = 0.031
no. of moles of NH4+ = 2×0.031 = 0.062
[NH₃] = no. of moles / volume(L) = 0.099/ 0.5 = 0.198
[(NH₄⁺] = 0.031/0.5 = 0.124
1) now we know that
pH + pOH = pkw
pOH = pkw - pH = 14 - pH ---- -1
also
pOH = pkb + log ( [salt]/[base])
from 1
14 - pH = pkb + log ( [salt]/[base])
putting values
14- pH = -log(1.8e-5) + log(0.124/0.198)
14 - pH = 4.54
pH = 9.45
2) if 0.88g NaOH is added then as we know that NaOH is a base then it will reduce the buffer capacity
as there would be OH- ions initially present
hence the buffer action will move backward
i.e
pOH = pkb + log {(salt-x) / (base+x)}
where x= molarity of NaOH
no of moles of NaOH = 0.88 / (23+16+1) = 0.022
molarity of NaOH = 0.022/0.5 = 0.044
then 14 - pH = -log(1.8e-5) + log{ (0.124-0.044) / (0.198+0.044) }
14 - pH = 4.26
pH = 9.74
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Describe the bodys first line of defense
Answer:
The main function of the immune system is to provide immunity to the body. Immunity is the body's ability to protect itself from the pathogens it is exposed to. Immunity depends on the body's ability to differentiate between things that belong in the body and those that do not. The immune system's first line of defense includes physical and chemical barriers that are always ready and prepared to defend the body from infection.
The skin acts as a barrier against pathogens. Some structures of the first line of defense include the skin, mouth, eyes, ears, nose, and stomach. The skin produces sweat and oil that work together to keep pathogens from the entering the body. Saliva and tears contain substances the can destroy pathogens. The ears and the stomach help fight pathogens.The ears produce ear wax that prevent pathogens from entering the ears. The stomach produces a liquid the kills pathogens.
Mucus is produce by the nose, lungs, throat, and stomach. Mucus traps pathogens. Mucus also prevent pathogens from getting into deep tissues. Anyway, the very first line of defense against any invasion of the human body is a set of physical barriers between the inside of the body and the outer world.
*my notes from edge2020*
Hope this helps ^-^
What volume of 12 M NaOH and 2 M NaOH should be mixed to get 2 litres of 9 M NaOH solution?
1. A 0.130 M solution of a weak base is titrated with a 0.130 M HCl solution. After the addition of 8.50 mL of the HCl solution to 25.00 mL of the weak base solution, the pH of the solution is 9.36 . Determine the pKb of the weak base.2. Calculate the pH of the resulting solution if 23.0 mL of 0.230 M HCl(aq) is added to (a) 33.0 mL of 0.230 M NaOH(aq).
Answer:
1. 4.93 = pKb of the weak base
2. pH = 12.61
Explanation:
1. When a weak base, B, is being titrated with HCl, the reaction occurs as follows:
B + HCl → BH⁺ + Cl⁻
That means the moles added of HCl are the moles of BH⁺ produced and moles of B are initial moles of B - Moles of HCl
Thus:
Moles B:
Initial moles:
0.0250L * (0.130mol / L) = 3.25x10⁻³ moles B
Moles HCl:
8.5x10⁻³L * (0.130mol / L) = 1.105x10⁻³ moles HCl
3.25x10⁻³ - 1.105x10⁻³ =
2.145x10⁻³ moles BMoles BH⁺ = Moles HCl:
1.105x10⁻³ moles BH⁺pH of the buffer made from B/BH⁺ is determined using H-H equation for weak bases:
pOH = pKb + log [BH⁺] / [B]
Where pOH is 14-pH = 14-9.36 = 4.64
pKb is pKb of the weak base, our unknown.
[BH⁺] could be taken as moles of BH⁺ = 1.105x10⁻³ moles
And [B] as moles of B = 2.145x10⁻³ moles B
Replacing:
pOH = pKb + log [BH⁺] / [B]
4.64 = pKb + log [1.105x10⁻³ moles] / [2.145x10⁻³ moles]
4.64 = pKb -0.288
4.93 = pKb of the weak base2. When HCl and NaOH are in solution the reaction that occurs is:
HCl + NaOH → H₂O + NaCl
To find pH we need to determine, first, which reactant is in excess:
Moles HCl:
0.023L * (0.230mol / L) = 5.29x10⁻³ moles
Moles NaOH:
0.033L * (0.0230mol / L) = 7.59x10⁻³ moles
That means NaOH is in excess and after the reaction will remain:
7.59x10⁻³ moles - 5.29x10⁻³moles = 2.3x10⁻³ moles NaOH = Moles of OH⁻
In 23+33mL = 56mL = 0.056L:
2.3x10⁻³ moles OH⁻ / 0.056L = 0.0411M [OH-]
As pOH = -log [OH-]
pOH = 1.39
pH = 14 - pOH
pH = 12.61Saturated solutions of which of these ionic compounds have the highest boiling point?A.Cd(OH)2 (Ksp = 5.9 x 10-15)B.Zn(OH)2C.Mg3(PO4)2D.AgNE.AgI(Ksp = 1.1 x 10-17) (Ksp = 1.0 x 10-25) (Ksp = 7.2 x 10-11) (Ksp = 8.5 x 10-17)
Answer:
D. AgN.
Explanation:
Hello!
In this case, since the boiling point of a solution increases are more solute remains dissolved in the liquid, as more energy is required to start the phase transition, for insoluble solids for which we know the solubility product which has the following relationship with the amount of ions in solution:
"the greater Ksp, the more ions the solution has"
In such a way, for the solid with the greatest Ksp we understand it has most of the ions in solution and therefore the highest boiling point, thus, among the choices, D. AgN is the one with the highest boiling point because it Ksp is 7.2E-11, whcih is the greatest.
Best regards!
Calculate the Molarity when a 6.11 mL solution of 0.1 H2SO4 is diluted with 105.12 mL of water
Molarity after dilution : 0.0058 M
Further explanationThe number of moles before and after dilution is the same
The dilution formula
M₁V₁=M₂V₂
M₁ = Molarity of the solution before dilution
V₁ = volume of the solution before dilution
M₂ = Molarity of the solution after dilution
V₂ = Molarity volume of the solution after dilution
M₁=0.1 M
V₁=6.11
V₂=105.12
[tex]\tt M_2=\dfrac{M_1.V_1}{V_2}=\dfrac{0.1\times 6.11}{105.12}=0.0058~M[/tex]
2. What group is Ballardium located? (Bu) *
Answer:
This question appears incomplete
Explanation:
There is no such element known as "Ballardium (Bu)" in the periodic table. However, there are elements with a bit of similarity in spellings and pronunciation such as Beryllium (Be) which is found in group 2 (meaning it is an alkali earth metal), Berkelium (Bk) which is an actinide (meaning it is radioactive) and Vanadium (V) which is found in group 5 of the periodic table (meaning it's a transition metal).
The initial concentration of NOCl in the second-order reaction 2NOClâ2NO+Cl2 is 0.878M. After 763,200 seconds, the concentration of NOCl is 0.83M. What is the rate constant k for the reaction? Report your answer in scientific notation rounded to two significant figures. Use the multiplication symbol when reporting your answer rather than the letter x. Provide your answer below: $$ 1/M s
Answer:
[tex]k=8.63x10^{-8}\frac{1}{M*s}[/tex]
Explanation:
Hello!
In this case, since the differential rate law of a second-order reaction is:
[tex]\frac{dC_A}{dt}=-kC_A^2[/tex]
Whereas A stands for NOCl and the corresponding integrated rate law is:
[tex]\frac{1}{C_A} =kt+\frac{1}{C_A_0}[/tex]
Thus, since we know the concentrations and the elapsed time, we compute the rate constant as shown below:
[tex]k=( \frac{1}{C_A}-\frac{1}{C_A_0} )/t\\\\k=( \frac{1}{0.83M}-\frac{1}{0.878M} )/763,200s\\\\k=8.63x10^{-8}\frac{1}{M*s}[/tex]
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Arrange the following compounds in order of increasing acidity, and explain the reasons for your choice of order. Enter your answer in the answer box below. a. 4-nitrophenol b. cyclohexanol c. 2,6-difluorocyclohexanol d. 4-bromophenol
Answer:
(a) > (d) > (c) > (b)
Explanation:
Acidic character is based upon inductive effect of the functional group that are attached to parent chain.
1. Nitro is a -I group which makes phenol acidic due to increased resonance, 2. bromine is a -I group but it is weaker than nitro group
3. phenol is more acidic than cyclohexanol due to resonance stabilization of resonance and among halogen F>Cl>Br>I is the order of acidity
4. cyclohexanol will be weakest as it is not associated with any -I groups here.
so the order of acidity will be
(a). 4-nitropheno > (d). 4-bromophenol > (c). 2,6-difluorocyclohexanol > (b). cyclohexanol
If 12.4 mol of Ne gas occupies 122.8 L, how many mol of Ne would occupy 339.2 L under the same temperature and pressure? Record your answer in scientific notation using 3 significant figures.
Answer:
3.43×10¹ mol
Explanation:
Given data:
Initial number of moles = 12.4 mol
Initial volume = 122.8 L
Final volume = 339.2 L
Final number of moles = ?
Solution:
The number of moles and volume are directly proportional to each other at same temperature and pressure.
Formula:
V₁/n₁ = V₂/n₂
Now we will put the values,
122.8 L/ 12.4 mol = 339.2 L / n₂
n₂ = 339.2 L× 12.4 mol / 122.8 L
n₂ = 4206.08 L.mol /122.8 L
n₂ = 34.3mol
In scientific notation:
3.43×10¹ mol
What mass of solid aluminum hydroxide is produced when 50.0 mL of 0.20 M aluminum nitrate is added to 200.0 mL of 0.100 M potassium hydroxide?
Answer:
0.52g of Al(OH)₃
Explanation:
The reaction of aluminium nitrate, Al(NO₃)₃, reacts with KOH, as follows:
Al(NO₃)₃ + 3KOH → Al(OH)₃ + 3 KNO₃
That means 1 mole of aluminium nitrate reacts with 3 moles of potassium hydroxide.
To find moles of aluminium hydroxide we need to determine the limiting reactant finding moles of each reactant:
Moles aluminium nitrate:
0.050L * (0.20mol / L) = 0.01 moles Al(NO₃)₃
Moles KOH:
0.200L * (0.100mol / L) = 0.02 moles of KOH
Thus, for a complete reaction of 0.02 moles of KOH are needed (Using the chemical equation)
0.02 moles of KOH * (1 mol Al(NO₃)₃ / 3 mol KOH) = 0.0067 moles of Al(NO₃)₃.
As there are 0.01 moles of Al(NO₃)₃, this is the excess reactant and KOH is the limiting reactant.
The 0.02 moles of KOH produce:
0.02 moles of KOH * (1 mol Al(OH)₃ / 3 mol KOH) = 0.0067 moles of Al(OH)₃
In mass (Using molar mass of Al(OH)₃: 78g/mol):
0.0067 moles of Al(OH)₃ * (78g/mol) =
0.52g of Al(OH)₃Which statement best describes evidence that a chemical reaction occurs as a cake bakes
Answer: the cake rises as gas bubbles form in the cake
Explanation: Had a quizziz quiz on this
Answer: The cake rises as gas bubbles form in the baking cake.
Explanation: had a test, got it right.
Give the location in the Periodic Table of Elements that have the same number of valence electrons.
All groups (columns) have the same number of valence electrons
All periods (rows) have the same number of valence electrons
All groups (columns), with the exception of Helium in the Noble Gases, have the same number of valence electrons
There is no trend found on the periodic table
Answer:
• All groups (columns) have the same number of valence electrons
Explanation:
Every group or column have the same number of valence electrons as a suprise. Every column is aligned in this way.
Answer:
all members within any group
Explanation:
A microwave operates at 7.42 mm wavelength. How much energy is produced in Joules from 359 photons?
answer numerically using scientific notation with e and significant figures.
Answer:
[tex]E=9.62\times 10^{-21}\ J[/tex]
Explanation:
Given that,
The wavelength of a microwave is 7.42 mm or 0.00742 m
No. of photons, n = 359
We need to find the energy produced by this no of photons. It can be given by the formula as follows :
[tex]E=\dfrac{nhc}{\lambda}\\\\E=\dfrac{359\times 6.63\times 10^{-34}\times 3\times 10^8}{0.00742}\\\\=9.62\times 10^{-21}\ J[/tex]
or
[tex]E=9.62e^{-21}\ J[/tex]
So, the required energy is [tex]9.62\times 10^{-21}\ J[/tex].
Answer:
⬆️That guy deserves brainliest
Explanation:
An organic chemist is planning to extract 1.00 g of an organic compound dissolved in 200.0 mL of water into a diethyl ether solvent. The partition coefficient for this system is 9.5, favoring the diethyl ether solvent. What percentage of the organic compound remains in the aqueous solvent if you perform three successive extractions with 50.0 mL of diethyl ether for each extraction?(a) 29.63% (b) 2.60% (c) 0.00169%
Answer:
(b) 2.60%
Explanation:
Partition coefficient of the organic compound in ether is:
9.5 = Concentration in ether / Concentration in water
In the first extraction, X is the amount of organic compound extracted:
9.5 = X/50mL / (1-X)/200mL
9.5 = 200X / (50-50X)
475 - 475X = 200X
475 = 675X
X = 0.7037g are extracted.
Remains = 1g - 0.7037g = 0.2963g
Second extraction:
9.5 = X/50mL / (0.2963-X)/200mL
9.5 = 200X / (14.815-50X)
140.74 - 475X = 200X
140.74 = 675X
X = 0.2085g are extracted.
Remains = 0.2963g - 0.2085g = 0.0878g
Third extraction:
9.5 = X/50mL / (0.0878g-X)/200mL
9.5 = 200X / (4.3899-50X)
41.70 - 475X = 200X
41.70 = 675X
X = 0.2085g are extracted.
Remains = 0.0878g - 0.0618g = 0.026g remains
Percentage: 0.026g / 1g * 100 =
(b) 2.60%unit factor method
convert a)26 cm in to meter
Calculate the heat change in kilocalories for condensation of 6.5 kg of steam at 100 ° C
Answer:
6,500 gm of steam require= 3,510 kilo calories (approx)
Explanation:
Every 1 gram of water at 100° C absorb 540 calories
So,
Total water = 6.5 kg = 6,500 gram
So,
6,500 gm of steam require = 6,500 x 540
6,500 gm of steam require= 3,510 kilo calories (approx)
According to the question,
Total water,
6.5 kg or 6,500 gTemperature,
100°CNow,
Required steam will be:
= [tex]6500\times 540[/tex]
= [tex]3510 \ kilo \ calories[/tex]
Thus the above answer is right.
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In addition to hydronium ions which type of ion do acids produce? (Choose all that apply)
A. Anion
B. A negative ion
C. Cation
D.A positive ion
Answer:
B
Explanation:
i just read it na, but i forgot the explanation
Answer:
A. and B.
Explanation:
Anion is negative as well as a negative ion.
(Just took the quiz)
What elements make up hydrogen peroxide?
Answer:
Hydrogen peroxide is a highly reactive chemical containing the elements hydrogen and oxygen. Pure hydrogen peroxide is a colourless liquid, but it is sold on the market as solutions in water, containing up to 33 – 37% pure hydrogen peroxide and other additives to stop the product decomposing.
Explanation:
Hope this helps <3
Which sentence is punctuated correctly? A. I bought all the ingredients for dinner, eggs, tomatoes, macaroni, and cheese and told Molly to preheat the oven. B. I bought all the ingredients for dinner: eggs, tomatoes, macaroni, and cheese—and told Molly to preheat the oven. C. I bought all the ingredients for dinner eggs, tomatoes—macaroni, and cheese and told Molly to preheat the oven. D. I bought all the ingredients for dinner (eggs, tomatoes), macaroni, and cheese and told Molly to preheat the oven.
The sentence that has an accurate punctuation is found in (Option B).
What are punctuation marks?The punctuation marks are those marks that are use to make a piece of writing to have a complete meaning. A piece of writing will be meaningless if there are no attached punctuation marks.
The sentence that is correctly punctuated is; "I bought all the ingredients for dinner: eggs, tomatoes, macaroni, and cheese—and told Molly to preheat the oven."(Option B)
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The inside window pane in your house feels very cold to touch on a winter night. How does the heat transfer?
Question 9 options:
A. Heat transfers from the window pane to your hand.
B. Heat transfers from your hand to the window pane.
Answer:
its B
Explanation:
Because its can only go cold to hot. -hope this help :)
Using the van der Waals equation, calculate the pressure for a 1.25 mol sample of xenon contained in a volume of 1.000L at 75°C; a = 4.194 L2 atm/mol2 and b = 0.05105 L/mol for Xe. Compare these results to that predicted by the ideal gas law.
Answer:
ABC
Explanation:
hrdjyt
Muscles in a kangaroo’s legs work because of the cells that make up the muscle. Which component of cell theory does this best illustrate?
( science )
Answer:
cells are a basic unit of structure and function all things
An energy bill indicates that the customer used 1024 kWh in July. How many joules did the customer use?
Answer:
3,686,400,000 Joules
Explanation:
Energy = 1024 kWh
To be converted to Joules.
The relationship between kwh and joules is;
1 kilowatt-hour = 3600000 J
So we have;
1 = 3600000
1024 = x
x = 1024 * 3600000
x = 3,686,400,000 Joules
What is the acceleration of a car moving at the same speed and in the same direction?
Answer:
if it ain't changing direction the acceleration isn't being affected
Give the location in the Periodic Table of Elements that have the same number of electron shells
all columns (groups) have the same number of shells
all periods (rows) have the same number of shells
only the transition metal elements have the same number of shells
Group VIII
Explanation:
All period have the same number of shells
PLS HELP!!!!
How do the products of chemical reactions compare to their reactants?
The products usually have more atoms than the reactants.
The products usually weigh more than the reactants.
The products often have completely different properties than the reactants.
The products are usually more toxic than the reactants.
How do the products of chemical reactions compare to their reactants?
Answer:
The products often have completely different properties than the reactants.
The correct answer to the question is: The products often have completely different properties than the reactants.
In a chemical reaction, the reactants and products of the reaction have different properties because during the reaction, bonds were broken and new bonds were formed which generate a new substance called the product.
However, chemical equations must be balanced in order to conform to the law of conservation of matter which states that matter can neither be created nor destroyed during a chemical reaction but can be transferred from one form to the other.
For example, the reaction of Hydrogen gas (H₂) and oxygen gas (O₂) to produce water (H₂O)
2H₂(g) + O₂(g) —> 2H₂O(l)From the equation, we can see that the reactants are gases but the product is a liquid which has a different properties from the gaseous reactants.
Therefore, the correct answer to the question is: The products often have completely different properties than the reactants.
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A ball has a kinetic energy of 4.50 kJ. If the ball has a mass of 120.0 g, how fast is the ball traveling, in meters per second?
Answer:
273.9m/s
Explanation:
Given parameter:
Kinetic energy of the ball = 4.5kJ
Mass of the ball = 120g
Unknown:
Speed of the ball = ?
Solution:
Kinetic energy of a body is the energy due to the motion of a body.
K.E = [tex]\frac{1}{2}[/tex] m v²
where m is the mass
v is the speed
Convert the quantities to the appropriate units;
4.5kJ to J = 4.5 x 10³J
120g to kg = 0.12kg
Now insert the parameters and find the unknown:
4500 = [tex]\frac{1}{2}[/tex] x 0.12 x V²
9000 = 0.12V²
V² = [tex]\frac{9000}{0.12}[/tex] = 75000
V = 273.9m/s