Explanation:
Elements heavier than Helium are synthesized in a number of environments. For elements that are lighter than Iron, those elements are synthesized during various phases in the evolution of massive stars. For elements heavier than Iron, one needs quite a bit of energy input to form these heavy elements.
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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3. Which of the rocks from the table would be classified as metamorphic rocks?
A.
Gneiss and slate, only
B.
Granite, only
C.
Limestone and basalt, only
D.
Coal, only
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!!
HELP GUYS PLEASE IM SUPPOSED TO ANSWER THIS VERY QUICKLY PLEASE
Answer:
Explanation:
It is b
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
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.
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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which of the following redox reactions do you expect to occur spontaneously in the forward direction? check all that apply.
a. Fe2+ + Cu2+ → Fe3+ + Cu+
b. Zn + Pb2+ → Zn2+ + Pb
c. Ag+ + Na → Ag + Na+
d. Cl2 + 2Na → 2NaCl
e. Mg + 2HCl → MgCl2 + H2
The reactions are expected to occur spontaneously in the forward direction; Fe²⁺ + Cu²⁺ → Fe³⁺ + Cu, Zn + Pb²⁺ → Zn²⁺ + Pb, Cl₂ + 2Na → 2NaCl, and Mg + 2HCl → MgCl₂ + H₂. Option A, B, D, and E are correct.
To determine which of the redox reactions are expected to occur spontaneously in forward direction, we will compare the standard reduction potentials of the involved species.
Fe²⁺ + Cu²⁺ → Fe³⁺ + Cu
For this reaction, the reduction potential of Fe²⁺ (-0.44 V) is lower than that of Cu²⁺ (+0.34 V). Therefore, the reaction will be expected to occur spontaneously in the forward direction.
Zn + Pb²⁺ → Zn²⁺ + Pb
The reduction potential of Zn (-0.76 V) is lower than that of Pb²⁺ (-0.13 V). Therefore, the reaction will be expected to occur spontaneously in the forward direction.
Ag⁺ + Na → Ag + Na⁺
The reduction potential of Ag⁺ (+0.80 V) is higher than that of Na (approximately -2.71 V). Therefore, the reaction is not expected to occur spontaneously in the forward direction.
Cl₂ + 2Na → 2NaCl
The reduction potential of Cl₂ (+1.36 V) is higher than that of Na (approximately -2.71 V). Therefore, the reaction is expected to occur spontaneously in the forward direction.
Mg + 2HCl → MgCl₂ + H₂
The reduction potential of Mg (-2.37 V) is lower than that of H⁺ (0 V). Therefore, the reaction is expected to occur spontaneously in the forward direction.
Based on the comparison of reduction potentials, the following reactions are expected to occur spontaneously in the forward direction;
Fe²⁺ + Cu²⁺ → Fe³⁺ + Cu
Zn + Pb²⁺ → Zn²⁺ + Pb
Cl₂ + 2Na → 2NaCl
Mg + 2HCl → MgCl₂ + H₂
Hence, A. B. D. E. is the correct option.
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How many moles of CaCO3 are needed to dissolve in 0.600 liters to make a
2.25 M solution?
A 0.267 mol
B 3.77 mol
C 1.35 mol
D 2.43 mol
Answer:
1.35 moles of CaCO₃
Explanation:
Molarity, it is a sort of concentration that indicates the amount of moles in 1 L of solution.
M = mol /L
This is a simple equation
M = 2.25 M
Our volume is 0.6L
M . L = mol
Then, 2.25 mol/L . 0.6L = 1.35 moles
We need 1.35 moles of CaCO₃
What type of scientists are the team at Stanford who are working to better understand Chinese Purple?A) ChemistsB) Materials C)Scientists D) Physicists
Han purple and Han blue are artificial barium copper silicate pigments that were created in China and utilized in ancient and imperial China beginning in the Western Zhou dynasty. They are also known as Chinese purple and Chinese blue. Chemists understand Chinese purple. The correct option is A.
Chemists create new, previously undiscovered substances as well as those that are naturally existing. Chemists research the characteristics of both organic and inorganic compounds. With the help of this knowledge, scientists can discover strategies to change certain compounds in order to make them more helpful.
Chemists carry out experiments in labs to analyze substances, create new goods, or enhance ones that already exist. They could focus on one or more fields, such as biochemistry, inorganic chemistry, or organic chemistry.
Thus the correct option is A.
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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 ?!
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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The dibasic compound B (pKb1 = 4.00, pKb2 = 8.00) was titrated with 1.00 M HCl. The initial solution of B was 0.100 M and had a volume of 100.0 mL. Find the pH at the following volumes of acid added and make a graph of pH versus Va; Va=0, 1, 5, 9, 10, 11, 15, 19, 20, and 22mL.
The pH values at various volumes of acid (HCl) added to the dibasic compound B can be determined based on its pKb values. By calculating the concentration of the species present at each volume, the Henderson-Hasselbalch equation can be used to find the corresponding pH values. A graph of pH versus the volume of acid added can be plotted using these calculations.
To find the pH at each volume of acid added, we need to consider the dissociation of the dibasic compound B and the resulting concentrations of its species. The pKb1 and pKb2 values indicate the equilibrium constants for the dissociation reactions. Initially, the volume of acid added is 0 mL, and the concentration of B is 0.100 M. At this point, B is fully ionized, and its concentration is 0 M. Therefore, the pH can be determined by calculating the concentration of OH- ions using the pKb2 value.
As acid (HCl) is added, it reacts with the B species. At each volume, the concentration of B, BH+, and BH2+ can be calculated based on the initial concentration and the volume of acid added. By applying the Henderson-Hasselbalch equation (pH = pKa + log([A-]/[HA])), the pH can be determined using the appropriate pKb value for each species. By repeating these calculations for each volume of acid added (1, 5, 9, 10, 11, 15, 19, 20, and 22 mL), the corresponding pH values can be obtained. These pH values can then be plotted against the volume of acid added to create a graph of pH versus Va.
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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.
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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Which of the following elements is the smallest?
Answer:
chlorine
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
What is the activation energy of this reaction?
50 kJ
100 kJ
150 kJ
200 kJ
Answer:
50 kJ
Explanation:
Activation energy is between the energy of reactants and the peak of the curve.
200 kJ - 150 kJ = 50 kJ
The correct answer is 50kJ
What is Activation Energy?The least amount of energy required to activate atoms or molecules to a state in which they can undergo a chemical reaction is known as Activation Energy.What is the activation energy of this reaction? The activation energy of this reaction is the energy released between reactants and productsIn graph the activation energy is difference between Reactants and the peakTherefore, 200-150=50KJ
Hence 50KJ is activation energy
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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
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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When dissolving a gas, an increase in pressure will result in a(n) ______________ in solubility.
Select what would most likely happen.
A. The plant population would increase; the fish population would increase.
B. The plant population would decrease; the fish population would increase.
C. The plant population would stay the same; the fish people would decrease.
D. The plant population would increase; the fish people would decrease.
5. A solution has a pH of 9. The solution is best described as:
Answer: Basic
Explanation:
A solution with a pH of more than 7 is considered basic.
What is the pH of a 1.0 x 10-2 M HNO3 solution?
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.
Magnesium oxide (mgo) has the rock salt crystal structure and a density of 3.58 g/cm3. the atomic weights of magnesium and oxygen are 24.31 g/mol and 16.00 g/mol, respectively. (a) determine the unit cell edge length.
Answer:
(a) The unit cell edge length 0.421 nm
Explanation:
Lets calculate -:
Given -
density = [tex]3.58g/cm^3[/tex]
Molecular weight of MgO = 24.31 +16
[tex]40.13 g/mole[/tex]
Avagadro number = [tex]6.022\times10^2^3[/tex]
In rock salt structure , there are four anions and four cations , hence Z=4 (Number of formula per unit cell)
Now, using the formula -
[tex]d=\frac{ZM}{N_Aa^3}[/tex]
[tex]a=[\frac{ZM}{N_Ad}]]^\frac{1}{3}[/tex]
Now, putting the given values
[tex]a=\frac{4\times40.13g/mole}{6.022\times10^2^3\times(3.58g/cm^3)}[/tex]
[tex]4.21\times10^-^8 cm[/tex]
= 0.421 nm
Hence , the unit cell edge length = 0.421 nm
The unit cell edge length of magnesium oxide (MgO) is equal to 0.421 nanometer.
Given the following data:
Density = 3.58 [tex]g/cm^3[/tex]Atomic weight of magnesium = 24.31 g/mol.Atomic weight of oxygen = 16.00 g/mol.Scientific data:
Avogadro's number = [tex]6.02 \times 10^{23}[/tex]Z for FCC = 4Molar mass of magnesium oxide (MgO) = [tex]24.31 + 16 = 40.31 \;g/mol.[/tex]To determine the unit cell edge length:
Mathematically, the unit cell edge length for a face-centered cubic (FCC) structure is given by the formula:
[tex]a=\sqrt[3]{\frac{ZM}{\rho N_A} }[/tex]
Where:
Z is the number of atoms per unit cell.[tex]\rho[/tex] is the density.M is the molar mass.[tex]N_A[/tex] is the Avogadro constant.Substituting the given parameters into the formula, we have;
[tex]a=\sqrt[3]{\frac{4 \; \times \;40.31}{3.58\; \times \;6.02 \times 10^{23}} }\\\\a=\sqrt[3]{\frac{161.24}{2.16 \times 10^{24}}}\\\\a=\sqrt[3]{7.47 \times 10^{-23}} \\\\a=4.21 \times 10^{-8}\;meter[/tex]
Note: [tex]1 \;nanometer = 1 \times 10^{-9} \;meter[/tex]
a = 0.421 nanometer.
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Which of the following is a large, burning ball of gas? (2 points)
a
Asteroid
b
Moon
c
Planet
d
Sun
Answer: D: sun
Explanation:
chemistry-mole calculations
Answer:
somebody answer this please>>>!!!
Explanation:
!!!
Complete the equation and indicate if a precipitate forms.
Li+(aq) + Br-(aq) + Pb2+(aq) + NO3-(aq) →
Answer:
Li⁺(aq) + 2Br⁻(aq) + Pb²⁺(aq) + NO₃⁻(aq) → PbBr₂(s) + NO₃⁻(aq) + Li⁺(aq)
A precipitate forms
Explanation:
To solve this question we must know the general solubility rules:
All group 1A (Li, Na, K...) and NH₄⁺ ions are always soluble.
The nitrates (NO₃⁻) and acetates are always solubles.
Cl⁻, Br⁻ and I⁻ are soluble except in the presence of Ag⁺, Pb²⁺, Cu⁺ and Hg₂²⁺
That means in the mixture of ions that we have, the Br⁻ will react with Pb²⁺ to produce PbBr₂(s):
Li⁺(aq) + 2Br⁻(aq) + Pb²⁺(aq) + NO₃⁻(aq) → PbBr₂(s) + NO₃⁻(aq) + Li⁺(aq)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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