What is the goal of mitosis? Of meiosis?
The isotope Yittrium-90 is used in nuclear medicine to treat cancer. It undergoes radioactive decay through beta emission.
a) Write a balanced nuclear reaction for the radioactive decay of Yittrium-90.
b) A patient was injected with a 2.5 mg sample of Yittrium-90. The half-life of Yittrium-90 decay by beta emission is 64 hrs. What is the activity at the start of the treatment?
c) For the treatment to be effective the activity of the radioactive isotope must be at least 50 Ci. Will the treatment dosage be effective for 1 week?
The treatment dosage will not be effective for 1 week.
A balanced nuclear reaction for the radioactive decay of Yittrium-90 (90 Y 39 ) is: 90 Y 39 ⟶ 90 Zr 40 + 0 β − 1b)Given dataMass of sample, m = 2.5 mgHalf-life, t1/2 = 64 hoursNumber of half-lives, n = t / t1/2 = 168 hours / 64 hours = 2.625Activity at the start of the treatment is given byActivity = A0 = m / (M × t1/2)Where, M = molar mass of the Yittrium-90 M = 90 gm/molActivity = A0 = 2.5 / (90 × 64 × 2.303) Ci = 0.00010175 Ci = 10.175 mCi ≈ 10.2 mCic)Activity of Yittrium-90 after 1 weekThe time duration of 1 week = 7 × 24 hours = 168 hoursThe initial activity of the Yittrium-90 at the start of treatment, A0 = 10.2 mCiThe half-life of Yittrium-90 decay by beta emission is 64 hours.Number of half-lives after 1 week is:n = t / t1/2 = 168 hours / 64 hours = 2.625The activity after 1 week = A0 / 2n = 10.2 / (2^2.625) mCi = 2.05 mCiThe activity of the radioactive isotope after 1 week of treatment is less than 50 Ci. Hence, the treatment dosage will not be effective for 1 week. Therefore, the treatment dosage is not effective for a week.
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chemistry-mole calculations
Answer:
somebody answer this please>>>!!!
Explanation:
!!!
balance
A FeS2 + B O2 → C Fe2O3 + D SO2 *
Answer:
4FeS2 + 6O2 > 2Fe2O3 + 8SO2
Explanation:
What are the two most recent fossils that have been found in New york?
cie
Explanation:cioserra s ojs queengo o m me vengoe volo
The diagram shows a large, eroded rock tower found in Southern Utah.
Which most likely caused the erosion?
C sunlight
O A animals
D. water
B. plants
A buffer solution is prepared by mixing 250 mL of 1.00 M nitrous acid with 50 mL of 1.00 M sodium hydroxide. Is the resulting solution a buffer solution? Yes or No? What is the pH of the resulting solution? The pKa of nitrous acid is 3.35.
Suppose an additional 0.05 moles of sodium hydroxide are added to our buffer solution. What is the change in pH due to the addition of the 0.05 moles of sodium hydroxide?
Yes, the resulting solution is a buffer solution. The pH of the resulting solution is 3.35. The change in pH due to the addition of 0.05 moles of sodium hydroxide is a decrease of 0.70 units, resulting in a new pH of 2.65.
Yes, the resulting solution is a buffer solution. A buffer solution is a solution that can resist changes in pH when small amounts of acid or base are added to it. In this case, the nitrous acid and sodium hydroxide react to form their conjugate acid-base pair, which can help maintain the pH of the solution.
To determine the pH of the resulting solution, we need to compare the concentrations of the conjugate acid (nitrous acid, HNO₂) and conjugate base (nitrite ion, NO₂⁻) in the buffer solution.
The Henderson-Hasselbalch equation is used to calculate the pH of a buffer solution
pH = pKa + log([conjugate base]/[conjugate acid])
Volume of nitrous acid (conjugate acid) = 250 mL = 0.250 L
Concentration of nitrous acid (conjugate acid) = 1.00 M
Volume of sodium hydroxide (conjugate base) = 50 mL = 0.050 L
Concentration of sodium hydroxide (conjugate base) = 1.00 M
pKa of nitrous acid = 3.35
[conjugate base] = concentration of sodium hydroxide = 1.00 M
[conjugate acid] = concentration of nitrous acid = 1.00 M
pH = 3.35 + log(1.00/1.00) = 3.35
Therefore, the pH of the resulting solution is 3.35.
For the second part of the question, if an additional 0.05 moles of sodium hydroxide are added, we need to determine the change in pH.
Since the volume of the solution remains the same, the final concentration of sodium hydroxide ([conjugate base]) will be
[conjugate base] = (initial moles of sodium hydroxide + additional moles of sodium hydroxide) / total volume
[conjugate base] = (0.050 moles + 0.05 moles) / (0.250 L + 0.050 L) = 0.20 M
Using the Henderson-Hasselbalch equation with the updated concentration of the conjugate base, we can calculate the new pH
pH = pKa + log([conjugate base]/[conjugate acid])
pH = 3.35 + log(0.20/1.00) = 3.35 - 0.699 = 2.65
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Zeke knows that there are several layers of sediment underneath his town. The top layer is soil, the next layer is clay, and the next layer is made up of gravel. He suspects that polluted water from a nearby mine is passing through one of these layers and making it into a local river. What could Zeke do to figure out how the polluted water might be moving from the mine to the river? A. He could build a model of the mine and test how deep it can go before it collapses. B. He could remove water from the mine and test it for certain pollutants. C. He could build a model of the soil layers and test if water passes through any of them. D. He could pour polluted water on the ground and test how long it takes for it to reach the river.
Answer:
He could add a model of soil layers.
Explanation: C
In an ecosystem where water from mine is polluting river it can be tested by building a model of the soil layers and test if water passes through any of them.
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.
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enzymes act as catalysts because they: group of answer choices decrease the enthalpy of the products. increase the entropy of the products.
Enzymes act as catalysts because they decrease the activation energy required to initiate a chemical reaction.
Why enzymes are considered as catalysts?Enzymes are molecules that accelerate chemical reactions by lowering the energy barrier (activation energy) for the transition state of the reaction. Enzymes bind to substrates, which are the reactants of the reaction.
The binding of the substrate to the enzyme lowers the energy required to transition the reactants to the transition state. This results in the lowering of activation energy that is required for a reaction to proceed
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please help me with these questions, im not understanding :(
Answer:
this is all the answers i hope you have a good day
Explanation:
may i please have a branlliests
please help I'm stuck
7. Which of the following correctly defines an acid-base reaction?
a. redox reaction
b. neutralization reaction
C. combustion reaction
d. hydrolysis reaction
Answer:
b
Explanation:
Energy pyramid worksheet
Pls help
Answer:
From top to bottom Jaguar, Toucan, Butterfly, and Hibiscus flower
Explanation:
Jaguars at the top because they eat toucans, Toucans eat butterflies, and butterflies eat hibiscus flower
which phrase describes the effect of adding a calyst to a chemical reaction in order to increase he reaction rate? a) uses the same reaction pathway with a higher activation energy b) provides a different reaction pathway with a lower activation energy c) uses the same reaction pathway with a lower activation energy d) provides a different reaction pathway with a higher activation energy
The correct phrase that describes the effect of adding a catalyst to a chemical reaction in order to increase the reaction rate is: (b) provides a different reaction pathway with a lower activation energy.
A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It achieves this by providing an alternative reaction pathway with a lower activation energy, making it easier for the reactant molecules to reach the transition state and proceed to form the products.
The catalyst itself is not permanently altered or consumed in the reaction and can participate in multiple reaction cycles, thereby increasing the overall reaction rate.
Overall, the presence of a catalyst alters the reaction kinetics by providing a different reaction pathway with a lower activation energy, resulting in an increased reaction rate.
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During strenuous exercise, lactic acid builds up in muscle tissues. In a 1.00 M aqueous solution, 2.94% of lactic acid is ionized. What is the value of Ka for lactic acid?
The value of Ka for lactic acid is approximately 0.0303. To find the value of Ka for lactic acid, we can use the ionization percentage and the initial concentration of the acid.
Given that 2.94% of lactic acid is ionized in a 1.00 M solution, we can calculate the concentration of the ionized form ([tex]CH_{3}CH(OH)COO-[/tex]) by multiplying the ionization percentage by the initial concentration of the acid: [[tex]CH_{3}CH(OH)COO-[/tex]] = 2.94% × 1.00 M = 0.0294 M
Since lactic acid ([tex]CH_{3}CH(OH)COO-[/tex]) is a monoprotic acid, the concentration of the undissociated form is equal to the initial concentration minus the concentration of the ionized form: [[tex]CH_{3}CH(OH)COOH[/tex]] = 1.00 M - 0.0294 M = 0.9706 M
The equilibrium expression for the ionization of lactic acid can be written as: Ka = [[tex]CH_{3}CH(OH)COO-[/tex]] / [[tex]CH_{3}CH(OH)COOH[/tex]]
Substituting the values, we get: Ka = 0.0294 M / 0.9706 M = 0.0303
Therefore, the value of Ka for lactic acid is approximately 0.0303.
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A reaction in which A,B, and C react to form products is zero order in A, one-half order in B and second order in C.
(b) What is the overall order of the reaction?
(c) By what factor does the reaction rate change if A is doubled (and the other reactant concentrations are held constant)? Express your answer numerically.
The overall order of the reaction is 2.5.
The reaction rate will not change if A is doubled,
What is the order of reaction?
We add together the individual orders of the reactants to get the reaction's overall order.
We have the following when the reaction has zero order in A, half order in B, and second order in C:
Order as a whole: 0 + 1/2 + 2 = 2 1/2 or 2.5
As a result, the reaction's overall order is 2.5.
We must comprehend how the response rate varies with the concentration of A in order to calculate the factor by which the rate changes when A is doubled. Doubling the concentration of A won't change the reaction's pace because the reaction is zero order in A.
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Enthalpy of
CH4(g) + 2NO2(g) -> N2(g) + CO2(g) + 2H2O(l)
Answer:
-177.9 kJ.
Explanation:
Use Hess's law. Ca(s) + CO2(g) + 1/2O2(g) → CaCO3(s) ΔH = -812.8 kJ 2Ca(s) + O2(g) → 2CaO(s) ΔH = -1269.8 kJ We need to get rid of the Ca and O2 in the equations, so we need to change the equations so that they're on both sides so they "cancel" out, similar to a system of equations. I changed the second equation. Ca(s) + CO2(g) + 1/2O2(g) → CaCO3(s) ΔH = -812.8 kJ 2CaO(s) → 2Ca(s) + O2(g) ΔH = +1269.8 kJ The sign changes in the second equation above since the reaction changed direction. Next, we need to multiply the first equation by two in order to get the coefficients of the Ca and O2 to match those in the second equation. We also multiply the enthalpy of the first equation by 2. 2Ca(s) + 2CO2(g) + O2(g) → 2CaCO3(s) ΔH = -1625.6 kJ 2CaO(s) → 2Ca(s) + O2(g) ΔH = +1269.8 kJ Now we add the two equations. The O2 and 2Ca "cancel" since they're on opposite sides of the arrow. Think of it more mathematically. We add the two enthalpies and get 2CaO(s) + 2CO2(g) → 2CaCO3(s) and ΔH = -355.8 kJ. Finally divide by two to get the given equation: CaO(s) + CO2(g) → CaCO3(s) and ΔH = -177.9 kJ.
helppppp will mark brainlest
Answer:
if you will decrease the HCO3- so the less H+ ion will be form and reaction will more likely shift to product and when HCO3- decreases pH value increases and vica versa for the increasing HCO3 the more H+ ion will be form and reaction will shift to product and the pH value will decreases!!
I've doubt in reaction shift coz whatever is the amount of HCO3- this is completely gonna form number of H+ so reaction shift may or may not be same!!
4 NH3 + 302
2N2 + 6H₂O
2.) a) A chemist burned 0.25 moles of ammonia gas (NH,) in the presence of excess oxygen
pps to produce 2.95 grams of nitrogen gas (N2). Calculate the theoretical yield of
nitrogen gas.
Answer:
this is hard
Explanation:
Answer:
I'm not sure but maybe 1 g ?!
For the following equilibrium, BaSO4(s) = Ba² + (aq) + S0 - (aq) if HCl is added, how will the quantities of each species change? Select the correct answer below: [Ba2+] increases, (so-1 decreases, mass of solid decreases O [Ba? +1 decreases, (so 1 decreases, mass of solid decreases [Ba? increases, so increases, mass of solid increases [Ba²+] decreases, (so increases, mass of solid increases
Adding HCl to the equilibrium BaSO4(s) ⇌ Ba²+(aq) + SO4²-(aq) will result in an increase in [Ba²+] and a decrease in [SO4²-]. The mass of the solid BaSO4 will also decrease.
When HCl is added, it dissociates into H+ and Cl- ions. The H+ ions react with the SO4²- ions from the dissociation of BaSO4, forming HSO4- ions and shifting the equilibrium to the right. As a result, more Ba²+ ions are released into the solution, leading to an increase in [Ba²+]. On the other hand, the decrease in [SO4²-] occurs because some of the SO4²- ions combine with H+ ions to form HSO4-. Since the equilibrium is being driven towards the products, the concentration of Ba²+ increases, [SO4²-] decreases, and the mass of the solid BaSO4 decreases.
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For the reaction
2S(s)+ 3O2\rightarrow 2SO3(g)
how many moles of SO3 can be produced from 6.0 g O2 and excess S?
Group of answer choices
none of these
0.28 mol SO3
4.0 mol SO3
0.25 mol SO3
0.13 mol SO3
To determine the number of moles of SO3 produced, we need to use the stoichiometry of the balanced equation.
The balanced equation tells us that 3 moles of O2 react with 2 moles of S to produce 2 moles of SO3. Therefore, the molar ratio between O2 and SO3 is 3:2.
To find the moles of SO3 produced from 6.0 g of O2, we need to convert the mass of O2 to moles using its molar mass. The molar mass of O2 is approximately 32 g/mol.
Moles of O2 = mass of O2 / molar mass of O2
Moles of O2 = 6.0 g / 32 g/mol
Moles of O2 = 0.1875 mol
Using the molar ratio, we can calculate the moles of SO3 produced:
Moles of SO3 = (0.1875 mol O2) x (2 mol SO3 / 3 mol O2)
Moles of SO3 = 0.125 mol
Therefore, the correct answer is 0.13 mol SO3.
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Occurs in many complex organisms such as plants, animals and fungi
Answer:
DNA
Explanation:
The eukaryotic cell participates in the formation of complex organisms and contains a nucleus, cytoplasmic organelles, and a cytoskeleton.
In a eukaryotic cell, DNA is contained in a compartment called the nucleus, which is enclosed by a membrane.The answer should be DNA based on the wording of the question. Hopefully this helped a little bit.
HELP GUYS PLEASE IM SUPPOSED TO ANSWER THIS VERY QUICKLY PLEASE
Answer:
Explanation:
It is b
Which of the following elements is a nonmetal?
a. Nitrogen
b. Sodium
c. Iron
d. Silver
e. Calcium
The required correct answer is Nitrogen
Explanation: The following elements is a nonmetal: Nitrogen.
Elements are pure substances that cannot be split into simpler substances through chemical methods. The chemical elements are arranged in the periodic table according to their atomic number, electron configurations, and chemical properties. Elements can be classified into three categories: metals, nonmetals, and metalloids.
Nitrogen is a nonmetal element. Nitrogen is a non-metallic chemical element that is a colorless, odorless, and tasteless gas that makes up the majority of Earth's atmosphere. Nitrogen has an atomic number of 7 and is designated by the symbol N.
The element nitrogen has a wide range of uses, including in fertilizers, explosives, rocket fuel, and organic chemistry, among other fields. Nitrogen is also used to preserve and package food products because it is an inert gas that does not react with most other compounds.
To summarize, Nitrogen is a nonmetal element. It is a colorless, odorless, and tasteless gas that makes up the majority of Earth's atmosphere. Nitrogen is used for a variety of purposes, including fertilizers, explosives, rocket fuel, and organic chemistry, among others.
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a 0.0280 m solution of an organic acid has an [h ] of 1.60×10-3 m .Using the values above, calculate the pH of the solution. What is the percent ionization of the acid? Calculate the Ka value of the acid.
The pH of the solution is 2.80, the percent ionization of the acid is 5.71%, and the Ka value of the acid is 9.14 × 10-5.
A.0280 M solution of an organic acid has an [H] of 1.60×10-3 M.Using the values above, the pH of the solution, the percent ionization of the acid, and the Ka value of the acid are given below:pH of the solution: The formula for calculating the pH of a solution is as follows:pH = -log[H] = -log[1.60 × 10-3] = 2.80Percent ionization of the acid:Percent ionization is given by the following formula:Percent ionization = ( [H+]/[HA] ) × 100 = (1.60 × 10-3/0.0280) × 100 = 5.71%Ka value of the acid:The formula for calculating the Ka value of an acid is as follows:Ka = [H+]2 / [HA]Ka = [1.60 × 10-3]2 / [0.0280]Ka = 9.14 × 10-5Hence, the pH of the solution is 2.80, the percent ionization of the acid is 5.71%, and the Ka value of the acid is 9.14 × 10-5.
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Which of the following are conjugate acid/base pairs? Select all that apply.
a. NaCl and NaOH
b. HCl and Cl-
c. H2SO4 and SO42-
d. H3PO4and H2PO4-
e. H2CO3 and CO32
The following are conjugate acid/base pairs:
HCl and Cl-.H2SO4 and SO42-.H3PO4 and H2PO4-.H2CO3 and CO32-.
Explanation:
In the acid-base reaction, the acid donates the proton (H+) while the base receives the proton. The substance that loses its proton becomes a conjugate base while the substance that gains a proton becomes the conjugate acid.
The conjugate acid/base pairs differ by one proton (H+).
NaCl and NaOH are not conjugate acid/base pairs as they are not acids or bases. NaOH is a strong base while NaCl is a neutral salt.
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How is structure linked to function?
please no upload files.
Answer:In biology, a key idea is that structure determines function. In other words, the way something is arranged enables it to play its role, fulfill its job, within an organism. Structure-function relationships arise through the process of natural selection.
A gas sample at 40° C occupies a volume of 3.22 L. If the temperature is raised to 55°C, what will the volume be, assuming the pressure remains constant?
Answer:
3.374L
Explanation:
According to Charle's Law:
V1/T1=V2/T2 (At constant pressure and moles)
where V=Volume and T=Temperature.
The temperature must be in kelvin.
K=C°+273
T1=40+273=313K
T2=55+273=328K
By applying the formula, we get:
3.22/313=V2/328
V2=(3.22*328)/313
V2=3.374L
Consider the equilibrium system described by the chemical reaction below, which has a value of Kc equal to 1.79 at a certain temperature. If a reaction mixture initially contains 0.050 M H2S and 0.050 M SO2, what will the equilibrium concentration of H20 be? 2 H2S(g) + SO2(g) ⇄ 3 S(s) + 2 H2O(g)
Equilibrium is a state of a reversible chemical reaction where the rates of forward and reverse reactions become equal, which results in the concentration of reactants and products being constant.
The chemical equation of the system described above is:2 H2S(g) + SO2(g) ⇄ 3 S(s) + 2 H2O(g)This system has an equilibrium constant (Kc) equal to 1.79 at a certain temperature. When the reaction mixture initially contains 0.050 M H2S and 0.050 M SO2, the equilibrium concentration of H2O can be found out as follows:As per the given equation, the mole ratio of H2S to H2O is 2:2 or 1:1. Therefore, the initial concentration of H2O is zero.The initial concentration of H2S is 0.050 M.Therefore, according to the equilibrium constant expression for this reaction, we can say that:[tex]\begin{align*}{K_c}&=\frac{\mathrm{[S]^3[ H_2O]^2}}{\mathrm{[ H_2S]^2[SO_2]}} \\ \\{1.79}&=\frac{\mathrm{(0.0.0.050)^2 [H_2O]^2}}{\mathrm{(0.050)^2 (0.050)}} \\ \\{1.79} \times \mathrm{(0.050)^3}&= \mathrm{[H_2O]^2} \\ \\{\mathrm{[H_2O]}}&= \sqrt{\mathrm{1.79} \times \mathrm{(0.050)^3}} \\ \\{\mathrm{[H_2O]}}&= \mathrm{0.027\ M} \end{align*}[/tex]Thus, the equilibrium concentration of H2O is 0.027 M.
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How is enthalpy related to the spontaneity of a reaction?
A. AH=0 contributes to spontaneity.
B. AH<0 contributes to spontaneity.
C. AH> 0 contributes to spontaneity.
D. AH does not affect spontaneity.
Answer:
D
Explanation:
Gibb's free energy change(∆G) and Standard electrode potential of electrochemical (Ecell) determine the spontaneity of a reaction.
when ∆G > 0, the reaction is not spontaneous
∆G < 0, the reaction is spontaneous
∆G = 0, the reaction is in equilibrium
when Ecell > 0, the redox reaction is spontaneous
Ecell < 0, the redox reaction is not spontaneous
Ecell = 0, the redox reaction is in equilibrium.
ΔH < 0 contributes to spontaneity.
What is a spontaneous reaction?A spontaneous reaction is one that takes place naturally under a certain set of circumstances. The general entropy, or chaos, of the system increases in the presence of spontaneous reactions.How can we determine if a reaction is spontaneous or not?We can determine it by calculating Gibb's free energy.
How do we calculate Gibb's free energy?It is calculated by the formula:
ΔG = ΔH - TΔS
ΔG is the change in Gibb's free energy,ΔH is the change in the enthalpyΔS is the change in entropy.How does ΔG tells if a reaction is spontaneous or not?If ∆G > 0, the reaction is not a spontaneous reaction∆G < 0, the reaction is a spontaneous reaction∆G = 0, the reaction is in equilibriumHow does ΔH contribute to the spontaneity of the reaction?For a reaction to be a spontaneous reaction, ∆G < 0.Consider a reaction, ΔG will be calculated as ΔH - TΔSIf ∆H < 0 then the ΔH - TΔS will be a lesser value ( more negative) than it would have been when ∆H = 0 or ∆H > 0.Therefore ∆H < 0 contributes to spontaneity.To learn more about ΔH, spontaneous reaction, enthalpy, and entropy here,
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True or False: Energy can be created.
А
True
B
False
Answer:
False
Explanation:
Scientifically, energy can never be created or destroyed. However it can be transfered. This law is called The Law of Conservation of Energy.