Explanation:
It is given that,
Initial orbit of electrons, [tex]n_i=4[/tex]
Final orbit of electrons, [tex]n_f=2[/tex]
We need to find energy, wavelength and frequency of the wave.
When atom make transition from one orbit to another, the energy of wave is given by :
[tex]E=-13.6(\dfrac{1}{n_f^2}-\dfrac{1}{n_i^2})[/tex]
Putting all the values we get :
[tex]E=-13.6(\dfrac{1}{(4)^2}-\dfrac{1}{(2)^2})\\\\E=2.55\ eV[/tex]
We know that : [tex]1\ eV=1.6\times 10^{-19}\ J[/tex]
So,
[tex]E=2.55\times 1.6\times 10^{-19}\\\\E=4.08\times 10^{-19}\ J[/tex]
Energy of wave in terms of frequency is given by :
[tex]E=hf[/tex]
[tex]f=\dfrac{E}{h}\\\\f=\dfrac{4.08\times 10^{-19}}{6.63\times 10^{-34}}\\\\f=6.14\times 10^{14}\ Hz[/tex]
Also, [tex]c=f\lambda[/tex]
[tex]\lambda[/tex] is wavelength
So,
[tex]\lambda=\dfrac{c}{f}\\\\\lambda=\dfrac{3\times 10^8}{6.14\times 10^{14}}\\\\\lambda=4.88\times 10^{-7}\ m\\\\\lambda=488\ nm[/tex]
Hence, this is the required solution.
f(Hz) = 6.17 × 10¹⁴
E(J) = 4.09 × 10⁻¹⁹
E(ev) = 2.56
Select the correct answer.
Which of these conditions would most likely cause a decrease in the population of any species?
ОА.
increased competition for resources
improved access to mates
OC.
elimination of predators
OD
decrease in pathogens
Answer(A increased competition for resources
Hope you get it right have a nice day
Answer:
A. increased competition for resources
Explanation:
What indicates how much of each reactant will be used up in a reaction?
A. The total moles of product
B. The molar mass of each element
C. The masses of final product
D. The coefficients of a balanced reaction
Answer:
D. The coefficients of a balanced reaction
Explanation:
Just took an a pex quiz
(I picked C and got it incorrect)
The coefficients of a balanced reaction. Hence, option D is correct.
What is a balanced equation?A balanced equation is a chemical reaction in which the number of atoms for each element in the reaction and oxidation numbers are the same for both the reactants and the products.
To adjust the substance condition, you need to ensure the number of molecules of every component on the reactant side is equivalent to the number of particles of every component on the item side.
To make the two sides equal, we need to duplicate the number of particles in every component until the two sides are equivalent.
Hence, option D is correct.
Learn more about balanced equations here:
https://brainly.com/question/7181548
#SPJ5
Which of the following is the best explanation for why it is important to follow lab safety guidelines
a. Following laboratory safety guidelines prevents all lab accidents.
b. Following laboratory safety guidelines minimizes the chance of lab ac
C. Following laboratory safety guidelines prevents fires.
d. Following laboratory safety guidelines allows quick response during la
Please select the best answer from the choices provided
Answer:
B
Explanation:
The main aim of lab rules is to minimize the no of accidents
What is the total energy change for the following reaction:CO+H2O-CO2+H2
Answer:
[tex]\large \boxed{\text{-41.2 kJ/mol}}[/tex]
Explanation:
Balanced equation: CO(g) + H₂O(g) ⟶ CO₂(g) + H₂(g)
We can calculate the enthalpy change of a reaction by using the enthalpies of formation of reactants and products
[tex]\Delta_{\text{rxn}}H^{\circ} = \sum \left( \Delta_{\text{f}} H^{\circ} \text{products}\right) - \sum \left (\Delta_{\text{f}}H^{\circ} \text{reactants} \right)[/tex]
(a) Enthalpies of formation of reactants and products
[tex]\begin{array}{cc}\textbf{Substance} & \textbf{$\Delta_{\text{f}}$H/(kJ/mol}) \\\text{CO(g)} & -110.5 \\\text{H$_{2}$O} & -241.8\\\text{CO$_{2}$(g)} & -393.5 \\\text{H$_{2}$(g)} & 0 \\\end{array}[/tex]
(b) Total enthalpies of reactants and products
[tex]\begin{array}{ccr}\textbf{Substance} & \textbf{Contribution)/(kJ/mol})&\textbf{Sum} \\\text{CO(g)} & -110.5& -110.5 \\\text{H$_{2}$O(g)} &-241.8& -241.8\\\textbf{Total}&\textbf{for reactants} &\mathbf{ -352.3}\\&&\\\text{CO}_{2}(g) & -393.5&-393.5 \\\text{H}_{2} & 0 & 0\\\textbf{Total}&\textbf{for products} & \mathbf{-393.5}\end{array}[/tex]
(c) Enthalpy of reaction [tex]\Delta_{\text{rxn}}H^{\circ} = \sum \left( \Delta_{\text{f}} H^{\circ} \text{products}\right) - \sum \left (\Delta_{\text{f}}H^{\circ} \text{reactants} \right)= \text{-393.5 kJ/mol - (-352.3 kJ/mol}\\= \text{-393.5 kJ/mol + 352.3 kJ/mol} = \textbf{-41.2 kJ/mol}\\ \text{The total enthalpy change is $\large \boxed{\textbf{-41.2 kJ/mol}}$}[/tex]
A platinum resistance thermometer has resistances of 160.0 when placed in a 0°C ice bath and 243.8 when immersed in a crucible containing a melting substance. What is the melting point of this substance? (Hint: First determine the resistance of the platinum resistance thermometer at room temperature, 20°C.)
Answer:
the melting point T = 125.36°C
Explanation:
Given that:
The resistance of a platinum thermometer at 0°C is [tex]R_o[/tex] = 160.0 ohms
The resistance of a platinum thermometer when immersed in a crucible containing a melting substance [tex]R_t[/tex] = 243.8 ohms
The temperature coefficient at room temperature 20°C = ∝ = 0.00392
The objective is to determine the melting point of this substance
To do that ; at 20°C, the resistance of the platinum thermometer can be calculated as follows:
[tex]R_{20} = R_o(1 + \alpha \Delta T)[/tex]
[tex]R_{20} = 160(1 + (0.00392 \times (20-0)^0C))[/tex]
[tex]R_{20} = 160(1 + (0.00392 \times (20))[/tex]
[tex]R_{20} = 160(1 + (0.0784)[/tex]
[tex]R_{20} = 160(1.0784)[/tex]
[tex]R_{20} = 172.544 \ ohms[/tex]
The resistance of the platinum thermometer at t°C , [tex]R_t[/tex] = [tex]R_{20}(1 + \alpha \Delta T)[/tex]
[tex]243.8 = 172.544(1 + 0.00392 \times (T-20)^0C}[/tex]
[tex]\dfrac{243.8}{ 172.544 }= (1 + 0.00392 \times (T-20)^0C}[/tex]
[tex]1.413 = (1 + 0.00392 \times (T-20)^0C}[/tex]
[tex]1.413-1 = 0.00392 \times (T-20)^0C}[/tex]
[tex]0.413 = 0.00392 \times (T-20)^0C}[/tex]
[tex]\dfrac{0.413 }{0.00392} = (T-20)^0C}[/tex]
105.36°C = (T - 20) °C
T = 105.36°C + 20 °C
T = 125.36°C
Select all the correct answers.
What does an increase in the temperature of air indicate?
Answer:
a.the air has less thermal energy so that the temperature increases
what is the valency of hydroxide
Answer:
Its valancy is 1.
As it has the formula OH-.
It has valancy 1.
hope it helps..
Which Group has different numbers of valence electrons?
A. Alkaline earth metals
B. Alkali metals
C. Transition metals
D. Halogens
Answer:
[tex]c. \: transition \: metals[/tex]Transition metals (Group C) have different numbers of valence electrons compared to the other groups mentioned. Therefore option C is correct.
Transition metals (Group 3-12) have varying numbers of valence electrons. This is because their valence electrons are located in more than one energy level or subshell.
The number of valence electrons for transition metals can range from 1 to 12, depending on the specific element within the group. The varying numbers of valence electrons in transition metals contribute to their diverse chemical properties and ability to form multiple oxidation states.
Therefore, transition metals (Group C) have different numbers of valence electrons compared to the other groups mentioned.
Know more about transition metals:
https://brainly.com/question/29828769
#SPJ2
why the filament of bulb has high melting point
Answer:
The filament of a bulb has a high melting point because of the heat generated inside the bulb.
Explanation:
When electricity is concentrating and run through a bulb, it starts to generate heat. Leave it on long enough and it will start to build up a lot of heat. Have you ever tried touching a light bulb when it has been all day? It's scorching to the skin.
Since electricity generates heat, the bulb's filament has to have a high melting point so it doesn't melt, destroy the bulb, and leave you light-less. If the filament has a high melting point, then it is able to withstand heat generated by electricity and provide you light.
What percentage of the total incoming radiation to the Earth reaches the ground? 20 30 40 70
Answer: 22.5 percent of incoming solar radiation goes directly to the surface of the Earth and is absorbed.
Explanation: Transfer of radiation through a planet's atmosphere. A planet and its atmosphere, in our solar system, can radiate back to space only as much energy as it absorbs from incoming solar radiation.
Answer:
Explanation:
I have the notes
"Only about 40 percent actually reaches the surface of the earth"
"our atmosphere and clouds reflect bout 40 percent of incoming solar radiation back into outer space"
"The remaining 60 percent is responsible for warming the earth"
"About 20 percent of this radiation is absorbed directly by the atmosphere"
What's the valency of sulphur for NaHSO4 and why?
Explanation:
According to the periodic table, it has 6 valance electrons in its outermost shell of an atom. so, the valancy must be 2.
we usually subtract the valancy from 8 to no. of electrons if no. of electrons in its outermost shell is more than 5.
so, 8-6=2
is the valancy of sulpher here.
Calculate mole fraction of ethylene
Glycol in solution
containing 20% g C2H6O2 by mass.
Answer:
Explanation:
20% of C2H6O2
since its a solution, this means that it has 20g of ethylene glycol and the rest is water.
Molar mass of C2H6O2 = (12 x 2) + (1 x 6) + (2 x 16)
= 62
mole = mass/molar mass
Moles of C2H6O2 = 20/62
= 0.322 mol
Moles of water = 80/18
= 4.444 mol
mole fraction = mol of solute / tatal mol of solution
Mole fraction of ethylene glycol = 0.322/(0.322 + 4.444)
= 0.068
Mole fraction of water = 1 - 0.068
= 0.932
When the name of ions end with ide, is it true that they are all negative ions
Help me pls!
What is heliuim?
Answer:
it's a chemical Element
Explanation:
symbol He
atomic number 2.
The reaction between hydrogen gas and chlorine gas produces hydrogen chloride according to the following equation: H2(g) + Cl2(g) → 2HCl(g). Using the following bond enthalpies(D) calculate the enthalpy of reaction. D(H-H) =436 kJ/mol; D(Cl-Cl) = 243 kJ/mol D(H-Cl) = 432 kJ/mol
Answer:
The enthalpy of reaction is -185 kJ
Explanation:
To get the reaction:
H₂(g) + Cl₂(g) → 2 HCl(g)
you must follow the following steps:
1) Reactive molecules must break their bonds to obtain their atoms.
H₂(g) → 2 H(g)
Cl₂(g) → 2 Cl(g)
Bond energy (or enthalpy) is the energy required to break one mole of bonds of a gaseous substance. In the case of diatomic molecules with a single bond, it corresponds to the energy necessary to dissociate 1 mole of said substance in the atoms that form it.
Whenever you want to break links you must supply energy, so the link enthalpy will have positive values; while when a mole of bonds is formed energy is released and the bond enthalpy of this process will be negative.
In this case you will then have:
H₂(g) → 2 H(g) ΔH=436 kJ/mol
Cl₂(g) → 2 Cl(g) ΔH=243 kJ/mol
So the total energy needed to break all the bonds is:
ΔH=1 mol*436 kJ/mol +1 mol* 243 kJ/mol= 679 kJ
2) The atoms that were obtained in the break of the bonds must be combined to obtain the product.
2 H (g) + 2 Cl (g) → 2 HCl (g)
Being the single bond energy for one mole of 431 kJ H-Cl bonds and considering that two moles of H-Cl bonds are formed, the ΔH is:
ΔH = -2 moles* (432 kJ/mol) = -864 kJ
As mentioned, when a mole of bonds is formed energy is released, the bond enthalpy of this process will be negative. So the formation of HCl is negative.
Hess's law states that the energy change in an overall chemical reaction is equal to the sum of the energy changes in the individual reactions comprising it. So:
ΔHtotal= -864 kJ + 679 kJ
ΔHtotal= -185 kJ
The enthalpy of reaction is -185 kJ
a 2.000-g sample of a hydrated copper sulfate is heated and the waters of hydration are removed if that mass of the remaining salt is 1.278 g what was the percentage of water in the original hydrate
Answer:
36.1%
Explanation:
The following data were obtained from the question:
Mass of hydrated copper sulfate = 2 g
Mass of anhydrous copper sulfate = 1.278 g
Percentage of water =..?
Next, we shall determine the mass of water in the hydrated copper sulfate.
This can be obtained as follow:
Mass of hydrated copper sulfate = 2 g
Mass of anhydrous copper sulfate = 1.278 g
Mass of water =...?
Mass of water = Mass of hydrated copper sulfate – Mass of anhydrous copper sulfate
Mass of water = 2 – 1.278
Mass of water = 0.722 g
Finally, we can obtain the percentage of water in the hydrated copper sulfate as follow:
Mass of water = 0.722 g
Mass of hydrated copper sulfate = 2 g
Percentage of water =..?
Percentage of water = mass of water /mass of hydrate x 100
Percentage of water = 0.722/2 x 100
Percentage of water = 36.1%
Therefore, the percentage of water in the hydrated copper sulfate is 36.1%
What are chemical changes of matter?
Answer:
Chemical Changes are also called Chemical Reactions. Chemical reactions involve combining different substances. The chemical reaction produces a new substance with new and different physical and chemical properties. Matter is never destroyed or created in chemical reactions.
Explanation:
A reaction is in equilibrium as shown: A + B C + D. Calculate the equilibrium constant in the final concentrations stabilized at: A= 9.6 M B= 10.0 M C= 4.0 M D= 4.0 M K =
Answer:
K = 0.167
Explanation:
The equilibrium constant, K of a reaction, is defined as the ratio of the concentrations of products and concentrations of reactants.
For the reactions:
A + B ⇄ C + D
For the definition, K is:
K = [C] [D] / [A] [B]
K = [4.0M] [4.0M] / [9.6M] [10.0M]
K = 0.167How will freezing the juice affect its mass?
Answer:
Mass increases since its going from liquid to solid.
Explanation:
Define the term “Tyndall effect”. Which of the following would show Tyndall effect:- (Starch solution, sodium chloride solution, alcohol and water mixture)
Answer:
Tyndall Effect is the phenomenon of scattering of light by particles in a colloid or in a very fine suspension.
Starch solution would show Tyndall effect.
N/B: Heterogeneous mixtures show Tyndall effect.
Answer:The Tyndall effect is light scattering by particles in a colloid or in a very fine suspension. Also known as Willis–Tyndall scattering, it is similar to Rayleigh scattering, in that the intensity of the scattered light is inversely proportional to the fourth power of the wavelength, so blue light is scattered much more strongly than red light. An example in everyday life is the blue colour sometimes seen in the smoke emitted by motorcycles, in particular two-stroke machines where the burnt engine oil provides these particles.
Under the Tyndall effect, the longer wavelengths are more transmitted while the shorter wavelengths are more diffusely reflected via scattering. The Tyndall effect is seen when light-scattering particulate matter is dispersed in an otherwise light-transmitting medium, when the diameter of an individual particle is the range of roughly between 40 and 900 nm, i.e. somewhat below or near the wavelengths of visible light (400–750 nm).
It is particularly applicable to colloidal mixtures and fine suspensions; for example, the Tyndall effect is used in nephelometers to determine the size and density of particles in aerosols and other colloidal matter (see ultramicroscope and turbidimeter).
It is named after the 19th-century physicist John Tyndall.
Explanation:
Escribe verdad o falso: La clorofila capta la energía luminosa del sol. () La fotosíntesis degrada las sustancias orgánicas que nesecitas las células()
Answer:
La clorofila capta la energía luminosa del sol. (verdadero) La fotosíntesis degrada las sustancias orgánicas que nesecitas las células(falso)
Explanation:
La clorofila es la encargada de dar el pigmento de color verde en las plantas y la que transforma la energia luminica en energia quimica, es por eso que es verdadera.
La fotosintesis NO degrada las sustancias organicas, sino que transforma un sustrato inorganico en una fuente energetica organica para las plantas.
Esto se debe por que las plantas o vegetales son autonomas, es decir que se autoabastecen energeticamente sin necesidad de ingerir alimentos como en el caso de los mamiferos.
A buffer solution contains 0.500 mole per liter each of acetic acid and sodium acetate. Determine the pH of the solution. The Ka of the acetic acid is 1.74 x 10-5. (Need an in-depth explanation with formulas please)
Answer:
The pH of the solution is 4.76
Explanation:
The concentration of the acetic acid and sodium acetate are 0.500 mole per liter each
The Kₐ of the acetic acid is 1.74 × 10⁻⁵
The concentration of the acetic acid CH₃COOH = 0.500 mole per liter = 0.5 M
The concentration of the sodium acetate (conjugate base) = NaCH₃COO = 0.500 mole per liter = 0.5 M
The dissociation constant, Kₐ, is given by the relation;
[tex]K_a = \dfrac{[H_3O^+][CH_3COO^-]}{[CH_3COOH]}[/tex]
Therefore, we have;
Kₐ × [CH₃COOH]/[CH₃COO⁻] = [H₃O⁺]
1.74×10⁻⁵×0.5/0.5 = 1.74 × 10⁻⁵
Therefore, [H₃O⁺] = 1.74 × 10⁻⁵
pH = -㏒₁₀(1.74×10⁻⁵) = 4.76
The pH of the solution = 4.76.
An object starts at position 12 on a horizontal line with a reference point of O. What is the position of the object if it
moves 14 units to the left?
O-26
O-2
O 2
O 26
Answer:
O-2
Explanation:
We assume your reference point is 12 units to the left of the position designated as 12. Then 14 unit to the left will be 2 units left of O, or O-2.
An object starts at position 12 on a horizontal line with a reference point of 0. What is the position of the object if it moves 14 units to the left?
THE ANSWER IS -2
List four examples of diffusion seen in daily life.
Answer:
Spraying perfume in one corner of the room and the smell travels to the other side of the room
Explanation:
which one of the following electronic configuration represents the element that forms simple ion with a charge of-3? (a)1s^2,2s^2,2p^6,3s^2,3p^1 (b)1s^2,2s^2,2p^6,3s^2,3p^3 (c)1s^2,2s^2,2p^6,3s^2,3p^6,3d^1,4s^2 (d)1s^2,2s^2,2p^6,3s^2,3p^6
Answer:
(b)
Explanation:
The 3s^2, 3p^6 orbitals form -3 charge.
This is the element phosphorous and an example of a -3 ion is in aluminium phosphide, AlP3.
The electronic configuration which represents the element forming a simple ion having with a charge of -3 is; 1s², 2s², 2p⁶, 3s², 3p³. Option B is correct.
In this electronic configuration, the element has a total of 16 electrons. To form a simple ion with a charge of -3, the element needs to gain three electrons. This is achieved by adding three extra electrons to the existing configuration.
When the element gains three electrons, the electron configuration becomes:
1s², 2s², 2p⁶, 3s², 3p⁶
This configuration represents the stable octet configuration, where the element has a complete outer shell with eight electrons. Since the charge is -3, it means the element has gained three extra electrons to achieve a stable configuration.
Therefore, the correct electronic configuration representing the element that forms a simple ion with a charge of -3 is 1s², 2s², 2p⁶, 3s², 3p³
Hence, B. is the correct option.
To know more about electronic configuration here
https://brainly.com/question/29184975
#SPJ2
What shape is represented by three bound groups and one lone pair around a
central atom?
A. Bent
B. Tetrahedral
C. Linear
D. Trigonal pyramidal
Answer:
D Trigonal pyramidal
Explanation went over in class:
Answer:
D. Trigonal pyramidal
Explanation:
A P E X !
As defined by Aristotle, which one of the following is an element?
1. water 2. air 3. soil 4. none of them
Answer:
4
Explanation:
none of them
they are compounds and mixtures
Answer:
4. none of them
Explanation:
Water is a compound.
Air is a mixture.
Soil is a mixture.
None of them are elements.
PLEASE HELP A woman travels to Canada where milk is sold in liters. She wants to buy enough milk at the grocery store to last 5 days and she knows at home she uses 0.75 gallons per week. How many liters must she buy?
Answer:
About 2 liters
Explanation:
Since 1 gallon equals 3.785 liters, you figure out how many liters per week she uses by 3.785 x 0.75 which is 2.83875. Then divide that by 7 which is 0.405535 liters per day. Then multiply that by 5 days which is 2.027 liters in 5 days.
5 people got tapped in an elevator due to electricty failure generator took 10 mins for being operational. Describe briefly changes in composition of air inside lift
Answer:
See the answer below
Explanation:
Since no fresh air is coming into the elevator while the people are still trapped in it, the breathing of the people will alter the composition of the air inside the lift.
Breathing involves taking-in of oxygen and the release of carbon dioxide. Hence, less and less oxygen will become available within the lift while the concentration of the carbon dioxide keeps increasing as time goes on.
If the people remain trapped for a long time, the oxygen composition of the air inside the elevator will become exhausted, the carbon dioxide concentration will increase, and the people will suffocate due to lack of oxygen.
The activation energy (E*) for 2N2O ---> 2N2 + O2 is 250 KJ. If the k for this reaction is 0.380/M at 1001oK, what will k be at 298oK? What will the half-life be at both temperatures?
Answer:
Explanation:
GIven that:
The activation energy = 250 kJ
k₁ = 0.380 /M
k₂ = ???
Initial temperature [tex]T_1 =[/tex] 1001 K
Final temperature [tex]T_2 =[/tex] 298 K
Applying the equation of Arrhenius theory.
[tex]In \dfrac{k_2}{k_1 }= \dfrac{Ea}{R}( \dfrac{1}{T_1 }- \dfrac{1}{T_2})[/tex]
where ;
R gas constant = 8.314 J/K/mol
[tex]In \dfrac{k_2}{0.380 }= \dfrac{250 * 10^3}{8,314}( \dfrac{1}{1001 }- \dfrac{1}{298})[/tex]
[tex]In \dfrac{k_2}{0.380 }= -70.8655[/tex]
[tex]\dfrac{k_2}{0.380 }= e^{-70.8655}[/tex]
[tex]\dfrac{k_2}{0.380 }= 1.67303256 \times 10^{-31}[/tex]
[tex]{k_2}= 1.67303256 \times 10^{-31} \times {0.380 }[/tex]
[tex]{k_2}= 6.3575 \times 10^{-32}[/tex] /M .sec
Half life:
At 1001 K.
[tex]t_{1/2} = \dfrac{In_2}{k_1}[/tex]
[tex]t_{1/2} = \dfrac{0.693}{0.38}[/tex]
[tex]t_{1/2} =[/tex] 1.82368 secc
At 298 K:
[tex]t_{1/2} = \dfrac{0.693}{6.3575 \times 10^{-32}}[/tex]
[tex]t_{1/2} =1.09 \times 10^{31} \ sec[/tex]