Answer:
how do I answer without context
based on the half-life of Tc-99, how many half-lives have to pass for a 150 mg sample of Tc-99 to decay down to 30mg?
Answer:
2.322 half-lives have passed to decay down from 150 miligrams to 30 miligrams.
Explanation:
The half of Technetium-99 is approximately 211000 years. The 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 isotope mass in time, measured in miligrams per year.
[tex]m[/tex] - Mass of the isotope, measured in miligrams.
[tex]\tau[/tex] - Time constant, measured in years.
Now we proceed to obtain the solution of this differential equation:
[tex]\frac{dm}{m} = -\frac{dt}{\tau}[/tex]
[tex]\int {\frac{dm}{m} } = -\frac{1}{\tau}\int dt[/tex]
[tex]\ln m = -\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.
The time passed for isotope is cleared within the equation described above:
[tex]\ln \frac{m}{m_{o}} = -\frac{t}{\tau}[/tex]
[tex]t = -\tau \cdot \ln \frac{m}{m_{o}}[/tex]
In addition, we can obtain the time constant 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} = 211000\,yr[/tex], [tex]m_{o} = 150\,mg[/tex] and [tex]m = 30\,mg[/tex], then the time passed is:
[tex]\tau = \frac{211000\,yr}{\ln 2}[/tex]
[tex]\tau \approx 304408.654\,yr[/tex]
[tex]t = -(304408.654\,yr)\cdot \ln \left(\frac{30\,mg}{150\,mg} \right)[/tex]
[tex]t \approx 489926.829\,yr[/tex]
The amount of passed half-lives is that time divided by a half-life. That is:
[tex]n = \frac{489926.829\,yr}{211000\,yr}[/tex]
[tex]n = 2.322[/tex]
2.322 half-lives have passed to decay down from 150 miligrams to 30 miligrams.
Which phrase describes neap tides?
A.) occur four times a day
B.) produce extra-low tidal ranges
C.) caused only by the pull of the moon
D.) occur at the same time as spring tides
NEED YOUR HELP.
Answer:
The answer is B
Explanation:
Neap tides are a type of to tie occuring after spring tides. It occurs when moon and sun are at the right angles to each other. It produce low tidal ranges. Hence, phrase B is correct.
What are tides ?Tides are a geographical phenomenon taking place due to the gravitational pull by sun and moon on the ocean of earth. They are long period waves causing the ocean back and forth to the cost.
During new moons larger tides appears in earth and they are called spring tides. Spring tides occurs twice in a lunar month. During spring tides, moon appears full and earth is between sun and moon.
After seven days of spring tide, lower tides are produced when the moo and sun comes in right angle to each other. They are called the neap tides producing lower range of tidal waves . During this time moon will be half full thus for the first and last quarter of the moon. Hence, the option B neap tide produce low tidal ranges is correct.
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Give an example of experimental bias
Answer:
chongus because he's the only good one
the kinetic molecules theory helps explain relastionships between
Answer:
hi :D
Explanation:
State the relationship between temperature and kinetic energy. The Kinetic Molecular Theory allows us to explain the existence of the three phases of matter: solid, liquid, and gas. In addition, it helps explain the physical characteristics of each phase and how phases change from one to another.
hope this helps
._.
...
The chemical formula for calcium chloride is
Answer: anhydrous CaCl 2 :0H 2 O
monohydrate CaCl 2 :1H 2 O
a di-hydrate CaCl 2 :2H 2 O
Explanation:
Which statement describes all chemical changes, but not all physical changes?
Answer:
A new substance forms.
Explanation:
Answer:
B
Explanation:
A flashbulb of volume 1.70 mL contains O2(g) at a pressure of 2.30 atm and a temperature of 18.0°C. How many grams of O2(g)
the flashbulb contain
Answer:
0.0001637 mol
Explanation:
PV = nRT
Very important formula in chem
2.3 atm * 0.0017 L = n * 0.082057 * 291 K
= 0.0001637 mol O2
This concept is very important in chem, practice it.
WHAT IS A NEWTON!! specifically the definition!!!!
Answer:
Explanation:
the SI unit of force. It is equal to the force that would give a mass of one kilogram an acceleration of one meter per second per second, and is equivalent to 100,000 dynes.
Describe what will eventually happen to the water level in the beaker.
Explain your reasoning.
Answer:
The water level in the beaker will eventually go down because some of the liquid water changes into ice (a solid) and the particles get closer together in the beaker. The water level in the beaker will eventually stay the same because some of the liquid water changes into water vapor (a gas) and leaves the beaker.
What change would you expect on the rate of the SN2 reaction of 1-iodo-2-methylbutane with cyanide ion if the nucleophile concentration is halved and the alkyl halide concentration is doubled
Answer:
The rate of reaction remains the same, no change is observed
Explanation:
Remember that for an SN2 reaction, the rate of reaction depends both on the concentration of the alkyl halide and the concentration of the nucleophile.
Hence we can write; Rate = k [Alkyl halide][NaI]
This implies that if we half the concentration of the nucleophile and double the concentration of the alkyl halide, the rate of reaction just remains the same since the reaction is bimolecular and first order in both alkyl halide and nucleophile
Briefly explain why the bulk temperature of the water remains low (at room temperature)
The diagram illustrates photosynthesis. Which best describes what is happening in the area marked X?
Answer:
You forgot to include the diagram use snipping tool to take a picture and upload it
Explanation:
how are compounds with metallic bonds similar to ionic compounds?
Answer:
Metals do not form double and triple bonds in general because metals want to lose electrons, not share, in order to become stable, and both compounds have high melting ppints
Compounds with metallic bonds and ionic compounds are similar in their melting point and boiling point, conductivity, solubility in polar solvents etc.
Ionic compounds are chemical compounds that are formed by the electrostatic attraction between oppositely charged ions.
Compounds with metallic bonds and ionic compounds are similar in several ways. Some of the similarities are:
1. High melting and boiling points: Both metallic and ionic compounds have high melting and boiling points due to the strong forces that hold the atoms or ions together.
2. Conductivity: Both metallic and ionic compounds are good conductors of electricity due to the presence of charged particles that can move freely.
3. Brittle: Ionic and metallic compounds are generally brittle in nature, meaning that they are prone to breaking or shattering when subjected to stress.
4. Solubility in polar solvents: Both metallic and ionic compounds are generally soluble in polar solvents such as water, due to the polar nature of the molecules.
In conclusion, compounds with metallic bonds and ionic compounds share several similarities. Both have high melting and boiling points, are good conductors of electricity, are brittle, and are generally soluble in polar solvents.
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A non polar covalent bond (pure covalent) would form in which of the following pairs of atoms?
A.) H-Cl
B.) Se-Br
C.) Na-Cl
D.) Br-Br
Consider the reaction when aqueous solutions of calcium nitrate and potassium carbonate are combined. The net ionic equation for this reaction is:
Answer:
Ca2+(aq) + 2OH-(aq) → Ca(OH) 2 ( s )
Explanation:
The balanced equation is given as;
Ca(NO 3 ) 2 ( aq ) + 2KOH(aq) → Ca(OH) 2 ( s ) + 2KNO 3 ( aq )
The net ionic equation features only ions that actually participated in the reaction. These ions are identified due to their change in oxidation numbers. Also, the aqueous compounds are broken down into ions.
Ca2+ + 2NO3- + 2K+ + 2OH- → Ca(OH) 2 ( s ) + 2K+ + 2NO3-
Ions present in both sides of the equation above. These are; NO3-, K+ and OH-
The net ionic equation is;
Ca2+(aq) + 2OH-(aq) → Ca(OH) 2 ( s )
Which one of these is not a characteristic of electromagnetic waves.
amplitude
wavelength
frequency
intensity
Answer:
Amplitude
Explanation:
Consider the following statements about first ionization energies:
I. Because the effective nuclear charge for Mg is greater than that for Be, the first ionization energy of Mg is greater than that of Be.
II. The first ionization energy of O is less than that of N because in O we must pair electrons in the 2p orbitals.
III. The first ionization energy of Ar is less than that of Ne because a 3p electron in Ar is farther from the nucleus than a 2p electron in Ne.
Which of the statements I, II, and III is or are true?
Answer:
I,II, III
Explanation:
Firstly, the magnitude of nuclear charge affects the first ionization energy of an element. Hence,as effective nuclear charge increases, the attraction between the nucleus and the outermost electron increases and ionization energy consequently increases. Thus Mg has a higher first ionization energy than Be.
Secondly, oxygen has an electron configuration of 1s2 2s2 2p4 while nitrogen has an electron configuration of 1s2 2s2 2p3. Now, recall that extra energy is often associated with half filled orbitals hence nitrogen has a higher first ionization energy than oxygen. Furthermore, the addition of electron to an already half filled 2p orbital in oxygen (pairing) leads to inter electronic repulsion and drastic fall in first ionization energy. Therefore, as we move from nitrogen to oxygen in the periodic table, greater inter-electron repulsion between two electrons in the same p-orbital counter balances the increase in effective nuclear charge hence nitrogen has a greater first ionization energy than oxygen.
Lastly, the 3p orbital is far away from the nucleus hence we expect it to feel less of nuclear attraction than a 2p orbital. Hence the first ionization energy of Ar is less than that of Ne.
Which statement accurately describes the atoms of a specific element? *
An indium, In, atom contains 115 protons inside the nucleus and 49 neutrons outside the nucleus.
A scandium, Sc, atom contains 45 electrons outside the nucleus and 21 neutrons inside the nucleus.
An aluminum, Al, contains 27 electrons and 27 protons inside the nucleus.
A zinc, Zn, atom contains 30 protons inside the nucleus and 30 electrons outside the nucleus
Answer:
the last one, (A zinc, Zn, atom contains 30 protons inside the nucleus and 30 electrons outside the nucleus)
A zinc, Zn, atom contains 30 protons inside the nucleus and 30 electrons outside the nucleus accurately describes the atoms of a specific element ,therefore option (d) is correct.
What are the characteristics of zinc element ?Zinc is placed in group 12 of the periodic table. It is in the first period of transition or d block elements, and fourth period of the periodic table.
Zinc is a metal. It has two valence electrons that are lost easily. Zinc forms positive ions with 2+ charges, like the metals of the alkaline earth family.
Uses of zinc element -:
Zinc is an important trace element for human beings. Zinc is used for making brass, an alloy of copper and zinc.Zinc is used as the anode in dry cells.A zinc, Zn, atom contains 30 protons inside the nucleus and 30 electrons outside the nucleus accurately describes the atoms of a specific element ,hence option (d) is correct.
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“An icy wind teetered trash cans and turned my cheeks to marble.”
What does the imagery in this sentence tell the reader about the weather?
in seedfolks
Given that one mole occupies 22.4 L at STP, show that R = .082 (atm * L)/(mol*K)
50 POINTS
Assume that the variables x and y are inversely related. If k = 18, what is the value of y for each of the following points?
Be sure and record your data to be used in the following problem.
х y k
1 18
A: 18,0.05,9
2 18
A: 0.11,36,9
3 18
A: 0.16,6,54
6 18
A: 0.33,108,3
9 18
A: 162,0.5,2
18 18
A: 324,0.75,1
Answer:
9/.05=180. I think it's 1
Explanation:
If x and y are inversely proportional then the product of xy =k or y=k/x
Watts are a measurement of power
Answer:
Watts are a measurement of power, describing the rate at which electricity is being used at a specific moment. For example, a 15-watt LED light bulb draws 15 watts of electricity at any moment when turned on. Watt-hours are a measurement of energy, describing the total amount of electricity used over time.
Please mark as brainliest.
Answer: True
Watts are a measurement of power, used in light bulbs and other electricity. It is also measured as candela (C) in SI Units. The answer to the question is true because of this measurement.
Hope this helps!
What is the same on the left and right side of a balanced equation? Explain your answer.
Answer:
Number of atoms of elements are same on left and right side of balance equation.
Explanation:
Every chemical reaction must follow the law of conservation of mass. According to which mass can neither be created nor destroy but it change from one to another form. It means mass remain conserved. That is why we need to balance the chemical equation because mass remain same on both side of equation. Consider the example,
Chemical equation:
N₂ + H₂ → NH₃
We can see that nitrogen and hydrogen react with each other and from ammonia. We need to balance the equation to have equal amount on both side.
Balance chemical equation:
N₂ + 3H₂ → 2NH₃
It means mass remain same but change from one to another form.
A balanced equation is one that is having a chemical reaction where the numbers of atoms. Here the number of elements in each reaction and the total charges are the same. This includes both the reactant and the product.
However, the mass and charge are balanced on both sides of the reaction. Hence the left and the right side is always equal to the number of atoms. Thus the chemical reaction is a balance of atoms involved in the reaction.Learn more about the same on the left and right sides of a balanced equation.
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A ___ reaction takes two or more reactants to make one product
Answer:
Synthesis
Explanation:
A sysnthesis reaction takes two or more reactants to create one product
How many protons and electrons does a hydrogen atom have?
A hydrogen atom contains 1 electron, 1 proton
Explanation:
If heat is required for a chemical reaction to occur, from where does the energy come?
Answer:
Chemical energy is energy stored in the bonds of chemical compounds, like atoms and molecules. This energy is released when a chemical reaction takes place. Usually, once chemical energy has been released from a substance, that substance is transformed into a completely new substance.
Explanation:
I WILL MARK YOU THE BRANLIEST!!!
Which property shows that electrons are quantized?
A. Electrons are attached to protons.
B. Each electron has its own "address."
C. Each electron carries a charge.
D. Electrons have very little mass.
Answer:
B. Each electron has its own "address."
Explanation:
This is the correct answer.
Good luck with the rest, and have a good day : )
Each electron has its own "address." Therefore, the correct option is option B among all the given options.
What is quantization?The elementary electric charge of the electron is a negative one, making it a subatomic particle. Due to their lack of components or substructure, electrons, which are part of the lepton particles family's first generation, are typically regarded to be elementary particles. The mass of an electron is roughly 1/1836 that of a proton.
The electron has a half-integer intrinsic rotational momentum that is represented in terms of the decreased Planck constant,, among its quantum mechanical features. The rule of exclusion developed by Pauli states that because electrons are fermions, no two of them may be in the same quantum state. Since they're capable of collide against other particles as well as can be bent like light, electrons, like all primary particles, display both wave and particle characteristics. Each electron has its own "address."
Therefore, the correct option is option B.
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Is the moons rate rotation that same as earths
Answer:
no
Explanation:
Answer:no
Explanation:The moon orbits the Earth once every 27.322 days. It also takes approximately 27 days for the moon to rotate once on its axis.
Why is H2S called an analytical agent?
Answer:
Hydrogen sulfide is an newly recognized signical molecule with very potent cytoprotective actions.
Which statement best describes how to predict the formula of a stable ionic compound? Use the same number of cations as anions so that the compound is neutral. Use more cations than anions so that the compound is positively charged. Use enough cations and anions so that the total charge is zero. Use fewer cations than anions so that the compound is negatively charged.
IT's C
Answer:
Option C: Use enough cations and anions so that the total charge is zero
Explanation:
In a stable ionic compound, to get a predict the formula, the positive and negative ions on one side need to cancel out so that the compound becomes neutral.
For example, let's take consider an ionic compound known as Potassium Chloride. It has a formula KCl. Now , breaking it down, the charges will be; K+ and Cl-. This means Potassium (K) has +1 charges and Chloride has -1 charges. Thus, they will cancel out to give a total neutral charge of 0.
Thus, the correct answer is to use enough a ions and cations so that the total charge is zero.
Answer:
C
Explanation:
edge 2020 unit rev