Which two models can be classified as elements
Answer:
First One And Third Pls Mark Brainlest
Explanation:
Radioactive isotope X has a half-life of 500,000 years. This isotope may be found in some types of volcanic rocks. A particular sample of volcanic rock taken from a layer that covered up some of the earliest known human-like footprints contains 0.125 mg of isotope X. The volcanic rock sample originally contained 8.00 mg of isotope X. How long ago were these footprints made. I need the equation. Thanks. please I am stuck on this question. PLEASE
Answer:
The age of the earliest known human-like footprints is approximately 3000000 years.
Explanation:
Decay of isotopes is represented by the following ordinary differential equation:
[tex]\frac{dm}{dt} = -\frac{m}{\tau}[/tex] (Eq. 1)
Where:
[tex]\frac{dm}{dt}[/tex] - First derivative of mass with respect to time, measured in miligrams per year.
[tex]m[/tex] - Current mass of the isotope, measured in miligrams.
[tex]\tau[/tex] - Time constant, measured in years.
Now we proceed to obtain the solution of the differential equation:
[tex]\int\limits {\frac{dm}{m} } = -\frac{1}{\tau}\int dt[/tex]
[tex]\ln m = -\frac{t}{\tau}+C[/tex]
[tex]m(t) = e^{-\frac{t}{\tau}+C }[/tex]
[tex]m(t) = m_{o}\cdot e^{-\frac{t}{\tau} }[/tex] (Eq. 2)
Where:
[tex]m_{o}[/tex] - Initial mass of the isotope, measured in miligrams.
[tex]t[/tex] - Time, measured in years.
[tex]\tau[/tex] - Time constant, measured in years.
We proceed to clear time within the formula presented above:
[tex]\ln \frac{m(t)}{m_{o}} = -\frac{t}{\tau}[/tex]
[tex]t = -\tau \cdot \ln \frac{m(t)}{m_{o}}[/tex]
In addition, time constant can be found as a function of half-life:
[tex]\tau = \frac{t_{1/2}}{\ln 2}[/tex] (Eq. 3)
If we know that [tex]t_{1/2} = 500000\,yr[/tex], [tex]m_{o} = 8\,mg[/tex] and [tex]m(t) = 0.125\,mg[/tex], the age of the earliest known human-like footprints is:
[tex]\tau = \frac{500000\,yr}{\ln 2}[/tex]
[tex]\tau \approx 721347.520\,yr[/tex]
[tex]t = -(721347.520\,yr)\cdot \ln \left(\frac{0.125\,mg}{8\,mg} \right)[/tex]
[tex]t \approx 3000000\,yr[/tex]
The age of the earliest known human-like footprints is approximately 3000000 years.
TIME REMAINING
58:36
The electron configuration for Helium (He) is shown below.
1s2
Which diagram shows the correct distribution of electrons in the electron shells of a helium atom?
Answer:
'*:*'
Explanation:
I know this looks weird, but
'= electron
*:* equals the nucleus, so 2 protons and 2 neutrons
and then '=electron
There are several ways to model a compound. One type of model is shown. A central C attached to 3 C's by 1 line each, each of the 3 C's being attached to 3 H's by a 1 line each. The central C is also attached by 1 line to a C, which is attached to 2 H's and a C by a single line each. The C is attached by 2 lines to an O ad by 1 line to another O. The O with 1 line is attached by 1 line to an H. What is the chemical formula for the molecule modeled? CHO C4H11O2 C6H12O2 C6H9O
Answer:
C6H12O2
Explanation:
The first step in accurately deducing the structure/formula of the model is to count the number of carbon atoms, hydrogen atoms and oxygen atoms mentioned in the model. This gives the molecular formula of the compound.
Next, you look at there arrangement of atoms and bonds as stated in the model, this tells us the structure of the molecule and confirms the molecular formula initially deduced.
The structure of the compound is shown below.
Answer:
Your answer would be C6H12O2
Explanation: I hope I helped you :)
A car travels at 35.0 mi/hr. How far has it gone in 2455 seconds?
Answer:
The answer is 23.8 milesExplanation:
The distance covered by an object given it's velocity and time taken can be found by using the formula
distance = velocity × timeFrom the question
velocity = 35.0 mi/hr
time = 2455 s = 0.68 hr
We have
distance = 35 × 0.68
We have the final answer as
23.8 milesHope this helps you
The capability of a substance to be stretched into thin wires without breaking is known as —
A malleability
B conductivity
C luster
D ductility
Answer:
The answer is D, ductility
Explanation:
The definition of ductile is "(of a metal) able to be drawn out into a thin wire."
HURRY I NEED HELP!! Please answer!!
Answer:
I'm confused on what u need us to answer
H2+ 02 H2O
how do you balence this
Answer:
As the number of atoms in the reactants side is equal to the number of atoms in the product side, the reaction is balanced
Two hydrogen molecules per oxygen molecule are produced because water (H2O) has a ratio of two hydrogen atoms to one oxygen atom. A decomposition reaction occurs when one reactant breaks down into two or more products. This can be represented by the general equation: AB → A + B.
H2O is the chemical formula of water. It means that each molecule of water is made up of two hydrogen atoms, indicated by the letter H, and a single oxygen atom, represented by the letter O. Water is chemical substance with no smell, taste or color.
Does Magnesium or Carbon have similar properties to Beryllium ? Which one ?
Answer:
Yes, Magnesium
2. Explain how energy originates and is emitted from a star.
Answer:
Stars generate energy through nuclear fusion. Here's an easy explanation about how the process works. ... Stars spend most of their lives repetitively compressing two hydrogen atoms into a single helium atom – plus a lot of energy, which is released as light and heat.
How many molecules are in 937 g of calcium acetate?
Answer:
158.17
Explanation:
divide the given mass by the molar mass
What two elements fill their last electron in the 5s sublevel?
Answer:Rubidium and Strontium
Explanation:
How much energy is required to heat 0.24 KG lutetium from 296.2K to 373.5 K? The specific heat for lutetium is 0.154 J/g-K
Answer:D. 2857 joules
Explanation:
Not going to lie I guessed but got it right
According to specific heat capacity, 3596.208 joules of energy is required to heat 0.24 kg of lutetium from 296.2 K to 373.5 K.
What is specific heat capacity?Specific heat capacity is defined as the amount of energy required to raise the temperature of one gram of substance by one degree Celsius. It has units of calories or joules per gram per degree Celsius.
It varies with temperature and is different for each state of matter. Water in the liquid form has the highest specific heat capacity among all common substances .Specific heat capacity of a substance is infinite as it undergoes phase transition ,it is highest for gases and can rise if the gas is allowed to expand.
It is given by the formula ,
Q=mcΔT
Substitution in above formula gives, q= 0.24×154×97.3=3596.208 Joules.
Thus, 3596.208 joules of energy is required to heat 0.24 kg of lutetium from 296.2 K to 373.5 K.
Learn more about specific heat capacity,here:
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Which iron pot has the least thermal energy?
A. A5 kg pot at 130°C
B. A 2 kg pot at 120°C
C. A 5kg pot at 25°C
D. A 2 kg pot at 25°C
Answer: D. A 2 kg pot at 25C.
Explanation:
Please answer correctly !!!!!!!!!!!!!!!!! Will mark brainliest !!!!!!!!!!!!!!!! And explain please !!!!!!!!!!!!
Hope this is your answer i wasn't able to see he full question so i am not sure
Which has the longest wavelength?
Which has the highest frequency?
Answer:
Which has the longest wavelength?
✔ microwaves
x infrared
x visible
x X-rays
Which has the highest frequency?
✔ X-rays
x infrared
x microwaves
x visible
Explanation:
I apologize if this was a late answer or if this doesn't answer your original question, but hope this helps! :)
Answer:
Microwaves then X rays
Explanation:
Which of the following pairs of elements belong to the same period?
Answer:
He and Ar
Explanation:
What is the correct lewis dot structure for
24
12Mg 2+?
Answer:
Mg with 2 dots
Explanation:
Mg: as the valnce shell of Mg has 2 electrons only
presented by 2 dots
help quick please?????
Answer:
the core
Explanation:
Answer:
3rd option, the core.
Explanation:
why does the uncertainty principle exist ?
Answer:
The uncertainty principle, proposed in 1927 by German physicist Werner Heisenberg, states that the more precisely a particle's position is measured, the less precisely its momentum can be known, and vice versa. ... They wanted to measure the polarization, or orientation, of the photon.
What affects the pressure of an object? *
Is wax ionic or covalent? why?
Answer:
Candle wax will melt to a liquid and burn as a gas. Only covalent compounds can be liquid or gas!
Explanation:
Question: Is Wax Ionic Or Covalent? - Ceramicsexpandusceramics.com
In the given question, wax is a covalent compound because it is composed of nonmetal atoms that share electrons to create covalent bonds.
Covalent compounds are formed when two or more nonmetal atoms share electrons in order to achieve a stable electron configuration.
Wax is made up of long-chain hydrocarbons, which are molecules that contain only carbon and hydrogen atoms. The carbon and hydrogen atoms in these molecules share electrons to form covalent bonds.Ionic compounds, on the other hand, are formed when a metal and a nonmetal react.Therefore, wax is a covalent compound because it is made up of non-metal atoms sharing electrons to form covalent bonds.
Learn more about covalent compounds here:
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Draw a heating curve for a solid
Pls pls helppppp
I will mark u as Brainly and award 30 points !!!!
Answer:
Equation:
Q = m•C•ΔT
A 5 kg block
is pulled across a table by a horizontal force of 4O N with a frictional force ot 8N pOsing the motion. Calculate the acceleration of the oject. 12 An ahia iddt
Answer:
By Newton's 2nd law, m*a=sum_of_forces where m is the mass and a the acceleration. Here there are two forces in opposed directions.
Thus 5*a=40-8=32 therefore a=32/5=6.4m^s/2
N(p+) = 12, N(n0) = 14, N(e-) = 10
Answer:
Mg[tex]^+2[/tex]
Explanation:
Es el elemento que buscas.
HELP PLEASE!!!
chemistry question
Answer:
Its going to be D) In sigma bonds the electrons are in the space between the joined atoms and pi bonds above and below the joined atoms
How many bromine atoms are present in 38.7 g of CH2Br2
Number of Br atoms : 2.679 x 10²³
Further explanationThe mole is the number of particles contained in a substance
1 mol = 6.02.10²³
Moles can also be determined from the amount of substance mass and its molar mass
[tex]\tt mol=\dfrac{mass}{MW}[/tex]
Proust stated the Comparative Law that compounds are formed from elements with the same Mass Comparison so that the compound has a fixed composition of elements
mass of Br in CH₂Br₂[tex]\tt mass~Br=\dfrac{2.Ar~Br}{MW~CH_2Br_2}\times mass~CH_2Br_2\\\\mass~Br=\dfrac{2.80}{174}\times 38.7=35.59~g[/tex]
mol of Br[tex]\tt \dfrac{35.59}{80}=0.445[/tex]
number of atoms[tex]\tt 0.445\times 6.02\times 10^{23}=\boxed{\bold{2.679\times 10^{23}}}[/tex]
Which statement is the best description of a chemical bond?
O A. A chemical bond connects 2 different molecules.
B. A chemical bond holds atoms together.
C. A chemical bond turns molecules into atoms.
D. A chemical bond identifies atoms in a molecule.
The answer Is B;A chemical bond holds atoms together.
Luciana explains to Eric how electricity flows in a circuit. Which sentences are a part of her explanation? Select all that apply.
A. Without a resistor, electricity cannot flow in a circuit.
B. Without a switch, electricity cannot flow in a circuit.
C. For electricity to flow in a circuit, the circuit must be complete.
D. An insulator such as plastic is needed for electricity to flow in a circuit.
E. A conductor is needed for electricity to flow in a circuit.
Answer:
E. A conductor is needed for electricity to flow in a circuit.
Explanation:
Electric current can flow without a resistor, as in short circuit.
A short circuit is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance.
Without a switch, electricity can flow in a circuit, switch is only used to close or open the circuit.
Thus, the only correct option is E
E. A conductor is needed for electricity to flow in a circuit.
19. Who was the first female astronomer
A.Aristotle
B.En Hedu’Anna
C.Archimedes
D.Plato
Answer: A.En Hedu'Anna
Answer:
En Hedu’Anna!
Explanation: