A radioactive isotope has a half-life of 10 minutes.
At the start of an experiment, the activity of a sample of this isotope was 800 counts
per second after allowing for background radiation.
Calculate how long it would be before the activity fell from 800 counts per second to
200 counts per second.
Answers
Answer: The time for activity to fell from 800 counts per second to 200 counts per second is 20 minutes
Explanation:
Expression for rate law for first order kinetics is given by:
\(t=\frac{2.303}{k}\log\frac{a}{a-x}\)
where,
k = rate constant
t = age of sample
a = let initial amount of the reactant
a - x = amount left after decay process
a) for finding the rate constant:
Half life is the amount of time taken by a radioactive material to decay to half of its original value.
\(t_{\frac{1}{2}}=\frac{0.693}{k}\)
\(k=\frac{0.693}{10min}=0.0693min^{-1}\)
b) for activity to fell from 800 counts per second to 200 counts per second.
\(t=\frac{2.303}{0.0693}\log\frac{800}{200}\)
\(t=20minutes\)
The time for activity to fell from 800 counts per second to 200 counts per second is 20 minutes
Related Questions
. At time t=0, an aluminum bar (thermal diffusivity k=0.86 ) of length Lcm with completely insulated lateral surfaces and constant thermal properties is removed from boiling water (uB=100 degrees Celsius). Do the following i), ii), iii) for each of the scenarios, a-d, below i) Write down the initial-boundary value problem. That is, the PDE along with any initial and boundary conditions. ii) Without solving for u(x,t), describe the temperature distribution in the bar as t→[infinity] based on physical intuition. iii) Find the solution as t→[infinity] by solving the appropriate steady state equation. a) The two ends of the bar are immediately immersed in a medium with constant temperature 10 degrees Celsius. b) The end at x=0 is immersed in a medium with temperature 0 degrees Celsius and the end at x=L is completely insulated.
Answers
(i) The initial-boundary value problem for the given scenarios are as follows:
a) Scenario a:
PDE: ∂u/∂t = k * ∂²u/∂x²
Initial condition: u(x, 0) = 100 (boiling water temperature)
Boundary conditions: u(0, t) = 10, u(L, t) = 10 (constant temperature at the ends)
b) Scenario b:
PDE: ∂u/∂t = k * ∂²u/∂x²
Initial condition: u(x, 0) = 100 (boiling water temperature)
Boundary conditions: u(0, t) = 0 (temperature at x=0), ∂u/∂x(L, t) = 0 (thermal insulation at x=L)
(iii) The solution for the temperature distribution as time approaches infinity can be found by solving the appropriate steady state equation.
What is the expected temperature distribution in the bar as time approaches infinity?(i) The initial-boundary value problem formulation states the partial differential equation (PDE) governing the temperature distribution in the aluminum bar, along with the initial condition and boundary conditions.
In scenario (a), both ends of the bar are immersed in a medium with a constant temperature of 10 degrees Celsius, while in scenario (b), the end at x=0 is immersed in a medium with temperature 0 degrees Celsius and the end at x=L is insulated.
(ii) As time approaches infinity, the temperature distribution in the bar tends to reach a steady state.
In scenario (a), the temperature throughout the bar will eventually approach a constant value of 10 degrees Celsius, since both ends are immersed in a medium with that temperature.
In scenario (b), the temperature at x=0 will approach 0 degrees Celsius, while the temperature at x=L will remain constant due to thermal insulation.
(iii) To find the solution as time approaches infinity, we need to solve the appropriate steady state equation.
In scenario (a), the steady state equation is ∂²u/∂x² = 0, which implies that the temperature gradient is zero throughout the bar, resulting in a constant temperature of 10 degrees Celsius.
In scenario (b), the steady state equation is ∂²u/∂x² = 0 with the boundary condition u(0) = 0, which implies a linear temperature distribution from 0 degrees Celsius at x=0 to a constant temperature at x=L due to insulation.
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the process of _____ determines a substance’s physical or chemical identity with as near absolute certainty as existing analytical techniques will permit.
Answers
The process of spectroscopy determines a substance's physical or chemical identity with as near absolute certainty as existing analytical techniques will permit.
Spectroscopy is the study of the interaction of electromagnetic radiation with matter and is a crucial tool in chemical analysis. By studying the spectrum of a substance (the way it absorbs, emits, or reflects light), spectroscopy can provide information about the composition, structure, and properties of the substance, thereby allowing for its identification with high accuracy.
Spectroscopy is a broad and interdisciplinary field that encompasses many different techniques for studying the interaction of electromagnetic radiation with matter. It plays a crucial role in various areas of science, including physics, chemistry, biology, and materials science. Spectroscopy provides information about the composition, structure, and properties of substances by analyzing the way they interact with light.
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The sodium atom loses an electron to form a sodium ion (Na+). Which statement is correct with respect to its atomic radius? A. The sodium ion has a larger radius than the atom. B. The sodium ion has a smaller radius than the atom. C. The sodium ion and the sodium atom radii are the same size. D. The sodium ion has twice the radius of the sodium atom.
Answers
Answer:B. The sodium ion has a smaller radius than the atom.
Explanation:
Because size of cation is less than neutral atom
what are fossil fuels?
Answers
A fossil fuel is a natural substance formed from the buried remains of ancient organisms that can be used as a source of energy. Fossil fuels formed over millions of years as heat and pressure from layers of sediment changed the decayed organic remains into materials such as coal and petroleum.
How are they made?Fossils fuels are usually made of fossilized plant and animal remains from millions of years ago. The creation of fossil fuels—either oil, natural gas, or coal—from these fossils is determined by the type of fossil, the amount of heat, and the amount of pressure which they bore.
Hope it helps....
(by Benjemin)
Fill in the two blanks
Answers
Answer:
A.) Longer and Shorter
Explanation:
If the wavelength of a light wave is shorter that means the frequency will be higher.
That means that longer wavelengths have a lower frequency.
1. Which would dissolve faster?
A. individual salt crystals
B. a big block of salt
2. most cases , when temperature increases , solubility
A. increases
B. decreases
3. As agitation increases , the rate at which a solute will dissolve
A. increases
B. decreases
Answers
1) A. individual salt crystals
2) A. increases
3) A. increases
hope this helps :)
A solution is defined as the homogeneous mixture which contain one or more solutes in a solvent. The factors which affect the solubility are temperature and pressure. Here individual salt crystals dissolve faster.
What is solubility?The maximum amount of solute which can dissolve in a given quantity of the solvent at a certain temperature is defined as the solubility. It is defined as the property exhibited by a material to dissolve in a given solvent.
The powdered salt found to dissolves faster in a solvent than the salt of larger size. The rate of dissolving is affected by the size of the solute. The faster the solute dissolves if its size is smaller. So the individual salt crystals dissolves faster.
In most cases, generally the solubility found to decrease with the increase of temperature. When the temperature increases, the kinetic energy of the molecules increases and thereby decreases the intermolecular force of attraction. The increase in the process of agitation decreases the solubility.
1. The correct option is A
2. The correct option is B
3. The correct option is B
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Which statement accurately describes humidity?
O Humidity is a measure of dew in the air.
O Colder air promotes more evaporation.
O Cold air holds more moisture than warm air.
O Humidity refers to the amount of water vapor in the air.
Answers
Humidity refers to the amount of water vapor in the air accurately describes it.
What is Water vapor?This can be defined as the gaseous phase of water as a result of heating in the atmosphere.
The amount of the water vapor in air is what is referred to as humidity which makes option D the most appropriate choice.
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PLEASE ANSWER FAST!!
Which statement best describes the seasonal changes of plants in the Michigan and Florida regions during the summer?
A. Summer in Michigan is a time of growth and maturity because more sunlight and water is available. In Florida, plants enjoy the same conditions, but for a longer period of time.
B. Summer in Michigan is a time when flowers begin to sprout and bloom throughout the season. In Florida, flowers are always in bloom due to milder winters.
C. The summers in Michigan and Florida are similar because in both regions the change to the landscape is a dramatic change from the spring season.
D. The summers in Michigan and Florida are similar because the plants in both regions end their periods of dormancy, trees start to grow buds, and plants begin to flower.
Answers
The summers in Michigan and Florida are similar because the plants in both regions end their periods of dormancy, trees start to grow buds, and plants begin to flower.
What are the effects of summer in plants in Michigan and Florida?Summer is a period of increased sunshine and usually results in increased in plant growth and development.
Florida experienced an increased sunshine in summer periods.
Similarly, in Michigan, plants grow abundantly in summer time.
Therefore, the summers in Michigan and Florida are similar because the plants in both regions end their periods of dormancy, trees start to grow buds, and plants begin to flower.
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can someone help me pls, it's abt things made with one type of matter all the way through. will give brain if it's a good answer
Answers
Answer: well there is a lot of examples that can be used but i feel like a good answer will be a flower peddle once broken its still a peddle but its either larger or smaller than what it originated. another example can be a tree. you can have many trees that are huge in size or you can have small ones. once snapped in half it will still be a tree but the size of the tree will not remane the same but it will still be a tree through and through
Explanation:
Why did workers form labor unions?
Answers
Answer:
Labor unions were created in order to help the workers with work-related difficulties such as low pay, unsafe or unsanitary working conditions, long hours, and other situations. ... Sometimes the unions organized strikes in order to try to change the conditions of the workers.
Explanation:
Answer:
to speak with one voice
Explanation:
a p e x
What is the nuclear charge on an atom of gold-197? ___________ (include the sign and magnitude)
Answers
The nuclear charge of gold will be +1.
The sum of all the protons' internal charges makes up the nuclear charge. Nuclear charge could be replaced with effective nuclear charge because this phrase takes the behavior of all electrons into consideration, whether they are part of the valence shell or just the inner shell.
Gold has 79 protons it its nucleus. and 118 neutrons . So, it will have one +1 charge .
Therefore, nuclear charge of gold will be +1.
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When an object is "hot," what can you say about the motion of its atoms?
Answers
Answer:
They atoms move around a lot and they are spread out, unlike the atoms in a cold object. The atoms in a cold object are compacted and only move a slight amount.
The following valence-shell configuration is possible for a neutral atom of a certain element. What is the element, and is this the ground state or an excited state of this element? ↑↓ ↑↓ ↑ ↓ 2s 2px 2py 2pz
element =
Is this the ground state or an excited state of this atom?
Answers
The element with the given valence-shell configuration is Carbon (C), and it is in the ground state.
The valence-shell configuration given represents the electronic configuration of a Carbon atom in the ground state. The notation ↑↓ represents the two electrons in the 1s orbital, while the notation ↑ and ↓ in the second shell (2s, 2px, 2py, and 2pz) represents the two electrons in the 2s orbital and the two electrons in each of the three 2p orbitals, respectively. Carbon has six electrons in its outermost shell, making it a member of the group 14 elements in the periodic table. The configuration is ground state since it represents the lowest energy state for the Carbon atom.
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When calcium reacts with chlorine, the reaction involves:
a. a transfer of electrons from Ca to Cl
b. the sharing of electrons between Ca and Cl
c. a creation of electrons
d. a transfer of electrons from Cl to Ca
Answers
When calcium reacts with chlorine, the reaction involves: a transfer of electrons from Ca to Cl. The correct option is (a).
In the reaction between calcium (Ca) and chlorine (Cl), the electrons are transferred from calcium to chlorine. This is indicated by the formation of calcium ions (Ca²⁺) and chloride ions (Cl⁻).
Calcium has two valence electrons in its outer shell, and chlorine has seven valence electrons. Calcium tends to lose its two electrons to achieve a stable configuration, while chlorine tends to gain one electron to achieve a stable configuration of eight valence electrons.
As a result, calcium loses two electrons, which are gained by chlorine. This transfer of electrons leads to the formation of calcium ions with a +2 charge and chloride ions with a -1 charge.
The option "a. a transfer of electrons from Ca to Cl" correctly describes the electron transfer that occurs during the reaction between calcium and chlorine.
This type of reaction, involving the transfer of electrons, is known as an ionic reaction and is characteristic of the formation of ionic compounds.
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give me the type of reactions ___ CuCO3 → ___ CuO + ___ CO2
Answers
When green copper carbonate{CuCO3} is heated it decomposes forming copper oxide {CuO} and carbon dioxide {CO2}. This is a decomposition reaction.
Chemistry HW
Name:
Gas Laws Practice Problems #1
1. A gas has a volume of 147 ml when its temperature is 42°C. What will the
temperature be when the gas has a volume of 100 mL?
Answers
The temperature when the gas has a volume of 100 mL will be approximately 28.6°C.
To solve this problem, we'll use Charles's Law, which states that the volume of a gas is directly proportional to its temperature when the pressure and the amount of gas are constant. The formula for Charles's Law is V1/T1 = V2/T2, where V1 and T1 represent the initial volume and temperature, and V2 and T2 represent the final volume and temperature.
Given: V1 = 147 mL, T1 = 42°C, V2 = 100 mL. Convert the Celsius temperatures to Kelvin: T1 = 42 + 273 = 315 K.
Now, we'll solve for T2:
(147 mL / 315 K) = (100 mL / T2)
T2 = (100 mL * 315 K) / 147 mL
T2 ≈ 214.3 K
Finally, convert back to Celsius: T2 = 214.3 - 273 ≈ 28.6°C.
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if only the concentration of n2(g) is increased the concentration of
Answers
If only the concentration of N2(g) is increased, the concentration of N2(g) will increase while the concentrations of other components of the reaction will remain the same.
The equilibrium constant, Kc, will also not change, but the reaction quotient, Qc, will increase.
Explanation:
Consider the following chemical equation:
N2(g) + 3H2(g) ⇌ 2NH3(g)
The balanced equation tells us that there are four moles of gas on the left side and two moles of gas on the right side.
As a result, the reaction shifts toward the right to balance the pressure if the volume is decreased, which means that the concentrations of all species rise.
On the other hand, increasing the concentration of N2(g) will cause the reaction to shift to the right, with an increase in NH3(g) concentration and a decrease in N2(g) and H2(g) concentrations, in order to reach equilibrium.
Example
Suppose that, at equilibrium, the concentration of NH3(g) is 0.50 M, the concentration of N2(g) is 0.100 M, and the concentration of H2(g) is 0.400 M.
In this situation, the equilibrium constant, Kc, is given as follows:
Kc = ([NH3(g)]2)/([N2(g)][H2(g)]3)Kc = ([0.50]2)/([0.100][0.400]3)Kc = 150
Now, let's suppose that only the concentration of N2(g) is increased to 0.200 M.
The new concentrations of H2(g) and NH3(g) can be determined using the reaction quotient, Qc, which is given as follows:
Qc = ([NH3(g)]2)/([N2(g)][H2(g)]3)
Qc = ([0.50]2)/([0.200][0.400]3)
Qc = 375
The reaction will shift to the right to decrease the reaction quotient and approach the equilibrium constant.
The new concentrations can be calculated using the equilibrium constant and the new concentration of N2(g):
Kc = ([NH3(g)]2)/([N2(g)][H2(g)]3)150
= ([NH3(g)]2)/([0.200][0.400]3)[NH3(g)]2
= 9.00 x 10-3[NH3(g)]
= 0.0950 MN2(g)
= 0.200 MH2(g)
= 0.350 M
The concentration of N2(g) has increased, and the concentrations of the other components have changed in order to maintain the equilibrium constant.
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HELPPPP!!! I need the CORRRECT answer
1.Which pair of properties describes the elements in Group 18?
a) They are gasseous at room tempature and chemically stable
b) they have 8 valence electrons and are stable
c) they are chemically stable and liquid at room tempature
d) they are magnetic and boil at room tempature
Answers
Answer: c
Explanation:
Describe the complete role of the acid catalyst in the dehydration of an alcohol.
Answers
The acid protonates the hydroxyl group and then the conjugate base deprotonates an adjacent carbon.
The final product of the alcohol dehydration reaction is an alkene. Dehydration of alcohols to alkenes occurs through the hydrogenation of alcohols using acid catalysts to form water. Describe the full role of the acid catalyst in the dehydration of alcohols. The acid protonates the hydroxyl group and then the conjugate base deprotonates the adjacent carbon.
Acid-catalyzed hydration is the addition of water to alkenes to form alcohols. The reaction proceeds stepwise and begins with the protonation of the double bond. Water itself is a weak acid and has a double bond. Acid catalysts are mainly used in organic chemical reactions. Many acids serve as a source of protons. Acids used for acid catalysis include hydrofluoric acid.
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Calculate the poh of this solution. round to the nearest hundredth. ph = 1.90 poh =
Answers
Answer:
10.25
Explanation:
There I proved it
Answer:
pOH = 12.10
Explanation:
pOH = 14 - pH = 14 - 1.90 = 12.10
The following reaction is a single-step, bimolecular reaction: CH3Br+NaOH--->CH3OH+NaBr. When the concentrations of CH3Br and NaOH are both 0.170 M, the rate of the reaction is 0.0090 M/s. (a) What is the rate of the reaction if the concentration of CH3Br is doubled? (b) What is the rate of the reaction if the concentration of NaOH is halved? (c) What is the rate of the reaction if the concentrations of CH3Br and NaOH are both increased by a factor of five?
Answers
(a) If the concentration of CH₃Br is doubled, the rate of the single-step, bimolecular reaction between CH₃Br and NaOH will also be doubled. Therefore, the new rate will be 0.018 M/s.
(b) If the concentration of NaOH is halved, the rate of the reaction will also be halved. Therefore, the new rate will be 0.0045 M/s.
(c) If the concentrations of CH₃Br and NaOH are both increased by a factor of five, the rate of the reaction will increase by a factor of five times five, which is 25. Therefore, the new rate will be 0.225 M/s.
The rate of a bimolecular reaction is proportional to the concentrations of both reactants raised to the power of one. This means that if the concentration of one reactant is doubled, the rate of the reaction will also double, while if the concentration of one reactant is halved, the rate of the reaction will also halve.
a. If the concentration of CH₃Br is doubled, the rate of the single-step, bimolecular reaction between CH₃Br and NaOH:
= 0.0090 M/s × 2 = 0.018 M/s
b. If the concentration of NaOH is halved, the rate of the reaction:
= 0.0090 M/s ÷ 2 = 0.0045 M/s
c. If the concentrations of CH₃Br and NaOH are both increased by a factor of five, the rate of the reaction:
= 5 × 5 = 25
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energy from motion and position.
from flocabulary
Answers
Energy gets from motion is called kinetic energy and energy due to position is called potential energy.
The energy that a body or particle gains as a result of its motion is known as kinetic energy.The effort necessary to accelerate an item to a random speed is known as kinetic energy.To comprehend fluid mechanics, liquid particles may be modelled using the kinetic energy equation that was developed for a body. Understanding the movement and heating of liquids in chemical industries requires knowledge of kinetic energy. Due to kinetic energy, the particles in a heated liquid move in a chaotic manner. Brownian motion refers to the random movement of particles in a liquid. According to Albert Einstein, the kinetic energy of the molecules' Brownian motion is exactly proportional to the temperature of a liquid. Temperature affects a substance's kinetic energy as well. whenever the substance's temperatureTo know more about kinetic energy visit : https://brainly.com/question/15764612
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5
A+
A-
What is John Doe's blood type? A drop of his blood w zoom in
placed into each of the four circles on this blood type card.
And A serum was
And 8 serum was added
added to this circle
to this circle
(no clump=no A
cho clumpano B protein)
protein)
No cumping in the control
B
B-
AB+
AB-
John Doe's
Blood Type:
Ant-Rh serum was
added to this circle
Clump = Rh protein
present
0+
Answers
Based on the information provided, it appears that John Doe's blood type is A-.
In the blood type card, John Doe's blood sample was placed in each of the four circles. A serum was added to one of the circles, and there was no clumping, indicating that there is no A protein present. 8 serum was added to another circle, but no information is given about clumping or lack thereof.
In the control circle, there was no clumping in the presence of B protein, suggesting that John Doe's blood type does not contain B antigen.
Lastly, in the Ant-Rh serum circle, there was clumping, indicating the presence of Rh protein. The "+" sign next to "0" suggests that John Doe is Rh positive (Rh+).
Putting all this information together, John Doe's blood type can be determined as A-.
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which shows how much electron is in the outer layer
Answers
Answer:
is there a picture or is it multiple choice?
a(n) _____ is an unstable physical mixture of undissolved particles in a liquid.
Answers
A "suspension" is an unstable physical mixture of undissolved particles in a liquid. A suspension is a type of mixture where small, solid particles are dispersed throughout a liquid, but they are not dissolved in the liquid.
These particles will eventually settle to the bottom of the container if left undisturbed, as they are not stable enough to remain suspended for long periods of time. Examples of suspensions include muddy water, blood, and paint. Suspensions can also be seen in pharmaceuticals, where active ingredients are suspended in a liquid medium for easier consumption.
It's important to note that suspensions can be distinguished from solutions, where the particles are fully dissolved in the liquid and do not settle over time. While suspensions may not be as desirable in some applications due to their instability, they can be useful in others, such as in providing targeted drug delivery to specific areas of the body.
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edit al least six lines to obtain energy
Answers
Answer:
Sure because of the gravity of the earth
How is the gravitational force related to the distance between two objects?
O It is directly proportional to the square of the distance.
O It is inversely proportional to the square of the distance.
OIt is directly proportional to the distance.
O It is inversely proportional to the distance.
Answers
The gravitational force is related to the distance between two objects because it is inversely proportional to the square of the distance.
What is the gravitational force?The gravitational force refers to the attraction between two different objects due to their masses.
This force (gravitational force) is fundamental for maintaining the distance of objects in the Universe.
In conclusion, the gravitational force is related to the distance between two objects because it is inversely proportional to the square of the distance.
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the liquid dispensed from a burette is called ___________. select one: solute analyte titrant water
Answers
The liquid dispensed from a burette is called Titrant.
When performing titrations, the liquid dispensed from a burette is known as the titrant, which is a solution of a known concentration used to react with a solution of unknown concentration. A burette is used in analytical chemistry to measure the volume of a liquid and to dispense measured quantities of a reagent. In acid-base titrations, the titrant is typically an acid or a base, while in redox titrations, the titrant is an oxidizing or reducing agent.
The liquid dispensed from a burette is added to the analyte solution until the reaction is complete and the endpoint is reached, indicating that the correct amount of titrant has been added to react with the analyte. The titrant is used to determine the unknown concentration of the analyte. In analytical chemistry, titrations are a common laboratory technique used to determine the concentration of a solution.
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is sugar made of tiny particles
Answers
to get an idea of the size of the parts of an atom, including the nucleus and the amount of space, the video segment compares a courtyard at cambridge university
Answers
The size of the parts of an atom, including the nucleus and the amount of space, can be difficult to visualize due to their incredibly small scale. To help provide an idea of their size, a video segment compares them to a courtyard at Cambridge University.
In this analogy, imagine the entire courtyard representing the entire atom. The nucleus, which is the central part of the atom, would be like a small statue placed in the middle of the courtyard. The rest of the space in the courtyard represents the electron cloud, which is the region where the electrons of the atom are found.
Overall, the video segment comparing the courtyard at Cambridge University to the parts of an atom is meant to give us a sense of the relative sizes of the nucleus and the electron cloud. It helps us understand that the nucleus is small and dense compared to the larger electron cloud surrounding it.
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