Answers
Related Questions
What is the solar radius of a main sequence star?
Answers
Answer:I'm going to give some fictitious values just so that we can get some perspective on the matter.
Let's say that the surface temperature of our sun is 10, the surface temp of the bigger star- the red giant formed from leaving the main sequence, has a temp of 0.2. of that- 2.
We can also say that the radius of our sun is 10, and the radius of the red giant is 1000. (100 times more)
Using the equation:
L
=
σ
A
T
4
σ
= The Stefan-Boltzmann constant =
5.67
×
10
−
8
But we can ignore the constant, as we are only interested in a ratio of these values.
L
S
u
n
=
4
π
(
10
)
2
×
10
4
=
1.26
×
10
7
L
S
t
a
r
=
4
π
(
1000
)
2
×
2
4
≈
2.01
×
10
8
2.01
×
10
8
1.26
×
10
8
≈
16
So the newly formed, red giant star is almost 16 times more luminous than the sun. This is owing to the increased surface area of the star due to the massively increased radius.
A small sidenote:
There is an equation that might be useful for comparing the radii, temperature and luminosity of main sequence stars. As red giants are not on the main sequence it could not be used here, but if you stumble across a question where they ask you to find the radius, luminosity or temperature given the other two, you can relate it to the sun's characteristics:
r
s
t
a
r
r
s
u
n
=
√
L
s
t
a
r
L
s
u
n
×
(
T
s
u
n
T
s
t
a
r
)
2
(I know, it's not a beauty to look at- but it works)
Where
X
s
u
n
is the radius, temperature, and luminosity of the sun. These are not often given in numerical values, but this equation serves well when asked to find e.g the radius of a star, in solar radii given that a star is twice as luminous and has 5 times the temperature of that of the sun.
Hence:
T
s
t
a
r
=
5
T
s
u
n
L
s
t
a
r
=
2
L
s
u
n
r
s
t
a
r
r
s
u
n
=
√
2
L
s
u
n
L
s
u
n
×
(
T
s
u
n
5
T
s
u
n
)
2
(cancel the common terms)
r
s
t
a
r
r
s
u
n
=
√
2
×
(
1
5
)
2
r
s
t
a
r
≈
0.057
r
s
u
n
(divide both sides by 0.0057)
17.5
r
s
t
a
r
≈
r
s
u
n
So the star's radius is almost 17.5 times that of the sun.
Hopefully, you find this info useful!
Explanation:
The density of pentanol, C3H20, is 0.8110 g/mL. Calculate the volume occupied by 7.455 moles of pentanol. What is the volume occupied by 7.455 moles of pentanol?
Answers
The volume occupied by 7.455 moles of pentanol is 553.5 mL or 0.5535 L.
What does molar mass of a compound signify?The molar mass of a given compound is the mass of one mole of that compound. It is expressed in unit as grams per mole (g/mol).
To calculate the volume of pentanol occupied by 7.455 moles of the substance, we can use the following formula:
Volume = (number of moles x molar mass) / density
The molar mass of pentanol (C3H8O) can be calculated as:
3 x atomic mass of carbon (12.01 g/mol) = 36.03 g/mol 8 x atomic mass of hydrogen (1.01 g/mol) = 8.08 g/mol 1 x atomic mass of oxygen (16.00 g/mol) = 16.00 g/mol Total molar mass = 60.11 g/mol
Placing the given values into the formula, we get:
Volume = (7.455 mol x 60.11 g/mol) / 0.8110 g/mL Volume = 553.5 mL or 0.5535 L
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There are two isotopes of an unknown element, X-19 and X-21. The abundance of X-19 is 14.55%. A weighted average uses the percentages of each isotope to scale their contribution to the total mass. Each isotope's contribution is the percentage (in decimal form) multiplied by the mass of the isotope. What is the contribution (in amu) to the weighted average from the X-19 isotope, which has a mass of 19.00 amu
Answers
Answer:
2.765amu is the contribution of the X-19 isotope to the weighted average
Explanation:
The average molar mass is defined as the sum of the molar mass of each isotope times its abundance. For the unknown element X that has 2 isotopes the weighted average is defined as:
X = Mass X-19 * Abundance X-19 + MassX-21 * Abundance X-21
The contribution of the X-19 isotope is its mass (19.00 amu) times its abundance (14.55% = 0.1455). That is:
19.00amu * 0.1455 =
2.765amu is the contribution of the X-19 isotope to the weighted average
kylie jenner wants to test if red or pink lipstick makes her lips look bigger. what is the independent variable here?
Answers
Answer:
her ugly duck lips
Explanation:
Answer:
her lips.
Explanation:
the dependent variable is the lip stick because it changes but her lips do not actually change at all, ......i think. ;)
mineral and nutrient solution is in water epiphyte plants or hydroponic plants
Answers
Answer:
hydro ponic plants
Explanation:
coz they are hydro
I need help ASAP pls
Answers
Answer:
A should be the swer n
Explanation:
Charcoal from the dwelling level of the Lascaux Cave in France gives an average count of 0.97 disintegrations of C-14 per minute per gram of sample. Living wood gives 6.68 disintegrations per minute per gram. Estimate the date of occupation and hence the probable date of the wall painting in the Lascaux Cave. (Half-life of C-14 is 5568 years)
Answers
Answer:
15502 years
Explanation:
From;
0.693/t1/2 = 2.303/t log [Ao]/[A]
Where;
t1/2 = half life of C-14
t = time taken
[Ao] = count rate of living sample
[A] = count rate of the charcoal under study.
0.693/5568 = 2.303/t log (6.68/ 0.97)
1.245 * 10^-4 = 2.303/t log (6.887)
1.245 * 10^-4 = 1.92998/t
t = 1.92998/1.245 * 10^-4
t = 15502 years
write the chemical equation of the reaction with a change in colour
Answers
Answer:
(i) Change in colour (ii) Change in temperature (iii) Formation of precipitate
Explanation:
(i) Change in colour: Reaction between lead nitrate solution and potassium iodide solution. Pb(NO3)2(aq)+2KI → PbI2(s)+2KNO3(aq) In this reaction, colour changes from colourless to yellow. (ii)Change in temperature: Action of dilute sulphuric acid on zinc. Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2 In this reaction, heat is evolved (iii) Formation of precipitate: Action of barium chloride on sodium sulphate. BaCl2(aq) +Na2SO4(aq) → BaSO4(s) +2NaCl(aq) BaSO4(s)
I need help can somebody help me
Answers
Answer:
they slow down
Explanation:
Water molecules slow down as they lose energy. The molecules become closer together and decrease the volume.
In the isotope Carbon-14, what does the number 14 represent?
Answers
Answer:
number of tamed protons and neutrons
Which of the following is a redox reaction?
A. CuO + H2SO4 → CuSO4 + H2O
B. 3MnO2 + 4A1 3Mn + 2A120,
C. MgCO, → MgO + CO2
D. Mg(OH)2 + 2HCl → MgCl2 +H20
Answers
Answer:
a
Explanation:
the answer to the question is a
Among the following chemical equations, redox reaction is [tex]3 MnO_2+4 Al\rightarrow 3 Mn +2 Al_2O[/tex].
The redox reaction can be defined as a reaction that involves the transfer of electrons between two species. Redox reactions comprise of two parts a reduced part and an oxidized part, which occur simultaneously . The part which is reduced gain electrons and hence there is a increase in oxidation state of the species.
While, the part which is oxidized looses electrons and hence there is a decrease in oxidation state of the species.During redox reactions, there is no net change in the number of electrons . Electrons which are given off in oxidation are used up in reduction.
Therefore, the correct option is B.
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Which of the following sentences uses commas correctly?
-----------------------------------------------------------------------------------------------------------------------------
I got all of the answers on the test correct, didn't I?
I, got all of the answers on the test correct didn't I?
I got all of the answers, on the test correct didn't I?
I got all of the answers on the test, correct didn't I?
Answers
An allergy medicine is usually stored in a cabinet at room termperature where its molecules move around each other. By
mistake, an intern transferred energy into the medicine. After one hour, the intern found the medicine and noticed that it
was a liquid. How were the molecules moving when the intern found the medicine? Explain why the molecules were
moving this way after the intern transferred energy ito the medicine.
Answers
Answer:
hello, can you pleas egive me the answer? i have the same exact question. thank you!
Explanation:
How many pounds of ice are required to absorb 4900 kJ of heat as the ice melts? The heat of fusion of water is 0.334 kJ/g.
help pls
Answers
Answer:
Q = ΔH fusion * mass (g)
when we have:
ΔH fusion (the heat (or enthalpy) of fusion = 0.334 kJ/g
and mass of ice = 22.4 g
so by substitution, we can get the energy (Q) required to melt this mass of ice:
∴ Q = 0.334KJ/g * 22.4 g
= 7.48 KJ
∴ the energy required to melt 22.4 g of ice is = 7.48 KJ
Explanation:
Glucose is the monomer in the natural polymers ____________________ and cellulose.
Answers
Answer:
Starch
I hope this helps
An adaptation is best described as occurring over which time scale? *
(10 Points)
O A. over many eras
O B. over many generations
O C. over one generation
D. over the lifetime of one individual
Answers
Answer:
over many eras
Explanation:
In an ecosystem, an adaptation is best described as occurring over many generations.
What is an ecosystem?Ecosystem is defined as a system which consists of all living organisms and the physical components with which the living beings interact. The abiotic and biotic components are linked to each other through nutrient cycles and flow of energy.
Energy enters the system through the process of photosynthesis .Animals play an important role in transfer of energy as they feed on each other.As a result of this transfer of matter and energy takes place through the system .Living organisms also influence the quantity of biomass present.By decomposition of dead plants and animals by microbes nutrients are released back in to the soil.
There are various types of ecosystem present in the environment.
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To date, scientific tests of astrology have never found that its predictive methods work.
True
False
Answers
true______________________
Which molecular compound is composed of the greatest number of atoms?
A. Carbon Dioxide
B. Dinitrogen Monoxide
C. Potassium Phosphide
D. Sodium Chloride
Answers
Answer:
Answer:
Potassium Nitride is composed of the greatest number of atoms.
Explanation:
find the number of atoms present in each compound we will write down their molecular formulas and then we will add up the number of atoms present in them.
A: Dinitrogen Monoxide:
Chemical formula of Dinitrogen Monoxide is N₂O. Therefore, it contains two atoms of Nitrogen and one atom of oxygen Hence, in total it contains 3 atoms.
B: Sodium Chloride:
Chemical formula of Sodium Chloride is NaCl. Therefore, it contains one atom of Sodium and one atom of Chlorine Hence, in total it contains 2 atoms.
C: Potassium Nitride:
Chemical formula of Dinitrogen Monoxide is K₃N. Therefore, it contains three atoms of Potassium and one atom of Nitrogen Hence, in total it contains 4 atoms.
D: Carbon Dioxide:
Chemical formula of Carbon Dioxide is CO₂. Therefore, it contains one atom of Carbon and two atoms of Oxygen Hence, in total it contains 3 atoms.
Explanation:
Aside from invasives like the crown-of-thorns starfish, what other factor is killing the Great Barrier Reef?
O increased temperatures
O overactive algae
O reactive forms of oxygen
O coral bleaching
Answers
Answer:
increased temperatures
Explanation:
The temperatures are increasing in the ocean because of ocean warming, by climate change. The heat in the ocean stresses healthy corals, which drains them of their vibrant colors, known as bleaching.
What kind of questions do scientists ask?
A. Ones that there are no right answers to
B. Ones that only deal with scientific issues
C. Ones that deal with matters of opinion
D. Ones that are answered through observing
Answers
ones that are answered through observing :)
Answer: D.
Explanation:
ones that are answered through observing.
How many atoms are in 12 moles of sodium?
Answers
Answer: There are 1.20 x 1024 atoms of sodium in 2 moles
Explanation:
If two-parent with AB blood group claim and say that they have a baby with O blood group is born to them and it is their own baby and not adopted. Do you think they are speaking the truth?
who knows this answer
Answers
How many moles are in 8.30 X 1023 molecules of H2O? with the step
Answers
Answer:
Answer: 1.38 moles
Explanation: According to Avogadro's law, 1 mole of every substance contains Avogadro number of particles (atoms, molecules or ions) i.e.6.023*10^23 particles.
Given : 1 mole molecule of water contains 6.023*10^23 molecules of water.
6.023*10^23 molecules are present in = 1 mole
8.30*10^23molecules will be present in =
1/6.023*10^23 ×8.30*10^23=1.38 moles
Thus molecules is equal to 1.38 moles.
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1. Fill in the blanks. Example: A nitrogen atom takes on a 3- charge when it forms an anion and becomes nitride. a. A magnesium atom takes on a ___ charge when it forms a(an) ____ion and becomes . b. A chlorine atom takes on a ___ charge when it forms a(an) ____ion and becomes . c. An oxygen atom takes on a ___ charge when it forms a(an) ____ion and becomes . d. A potassium atom takes on a ___ charge when it forms a(an) ____ion and becomes .
Answers
Answer: a. +2, cation and magnesium ion .
b. -1, anion, chloride
c. -2, anion, oxide
d. +1. cation , potassium ion
Explanation:
When an atom accepts an electron negative charge is created on atom and is called as anion.
When atom loses an electron positive charge is created on atom and is called as cation.
Magnesium (Mg) with atomic number of 12 has electronic configuration of 2,8,2 and thus it can lose 2 electrons to form [tex]Mg^{2+}[/tex] cation and becomes magnesium ion.
Chlorine (Cl) with atomic number of 17 has electronic configuration of 2,8,7 and thus it can gain 1 electron to form [tex]Cl^{-}[/tex] anion and becomes chloride.
Oxygen (O) with atomic number of 8 has electronic configuration of 2,6 and thus it can gain 2 electrons to form [tex]O^{2-}[/tex] anion and becomes oxide.
Potassium (K) with atomic number of 19 has electronic configuration of 2,8,8,1 and thus it can lose 1 electron to form [tex]K^{+}[/tex] cation and becomes potassium ion.
How does a temperature increase cause the rate of a reaction to increase?
A. It increases the kinetic energy of the molecules.
B. It decreases orientation requirements of the molecules.
C. It increases the equilibrium constant for the reaction.
D. It decreases the activation energy of the reaction.
Answers
Answer:
B
Explanation:
"The temperature increases cause the rate of a reaction to increases the kinetic energy"
What is rate of reaction?
The reaction rate, also known as the rate of reaction, is the rate for which a chemical reaction occurs, and is proportional to increase in product concentration per unit time and the reduction in reactant concentration per unit time. The rate of reaction varies greatly.
What is kinetic energy?
An object's kinetic energy is the energy it has as a result of its motion. It is the amount of work required to push a body of a given mass from rest to a certain velocity. The body keeps its kinetic energy gained during acceleration unless that speed changes.
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Question 10 of 35
A red blood cell can be used to model a typical animal cell.
What would happen to a red blood cell placed in very salty water?
O A. It would stay the same size because salt cannot cross the cell
membrane.
B. It would swell and burst as water moves into the cell, where there
is a higher concentration of water.
C. It would swell and burst because salt would be transported across
the cell membrane.
O D. It would shrink as water moves out of the cell to where there is a
lower concentration of water.
Answers
Suppose that X represents an arbitrary cation and that Y represents an anionic species. Using the charges indicated in the superscript of X and Y, fill in the remaining blanks below by writing the appropriate subscript for each X and Y to balance the net charge on the ionic XaYb compound formed (where a and b represent positive, whole numbers of X and Y, respectively).
Y- Y2- Y3-
X+
X2+ XY2
X3+
Answers
Answer:
See explanation.
Explanation:
Hello!
In this case, when having the cationic and anionic species with the specified charges, in order to abide by the net charge rule, we need to exchange the charges in the form of subscripts and without the sign, just as shown below:[tex]X^{m+}Y^{n-}\rightarrow X_nY_m[/tex]
Thus, for all the given combinations, we obtain:
- Y⁻
[tex]X^+Y^-\rightarrow XY\\\\X^{2+}Y^-\rightarrow XY_2\\\\X^{3+}Y^-\rightarrow XY_3[/tex]
- Y²⁻
[tex]X^+Y^{2-}\rightarrow X_2Y\\\\X^{2+}Y^{2-}\rightarrow X_2Y_2\rightarrow XY\\\\X^{3+}Y^{2-}\rightarrow X_2Y_3[/tex]
- Y³⁻
[tex]X^+Y^{3-}\rightarrow X_3Y\\\\X^{2+}Y^{3-}\rightarrow X_3Y_2 \\\\X^{3+}Y^{3-}\rightarrow X_3Y_3\rightarrow XY[/tex]
Best regards!
What happens when an electron jumps from energy level 1 to energy level 2 in an atom?
Answers
Which half reaction is associated with the anode?
Sn(s) —> Sn2+ (aq) + 2e-
Sn2+ (aq) + 2e- → Sn(s)
Pb2+ (aq) + 2e-->Pb(s)
Pb(s)->Pb2+ (aq) + 2e-
Answers
Answer:
vgf
Explanation:
Answer:
its either A or B
Explanation:
took the test twice and guessed LOL
its not C or D :>
What mass of KNO, will dissolve in 100 g of water at 100°C?
Answers
Answer:
About 170-180 grams of potassium nitrate are completely dissolved in 100 g.
Explanation:
Hello!
In this case, according to the reported solubility data for potassium nitrate at different temperatures on the attached picture, it is possible to bear out that about 170-180 grams of potassium nitrate are completely dissolved in 100 g; considering that the solubility is the maximum amount of a solute that can be dissolved in a solvent, in this case water.
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