Answer:
1.49 × 10⁹ years
Explanation:
Step 1: Calculate the rate constant (k) for the nuclear decay of U-235
The decay follows first-order kinetics with a half-life (t1/2) of 703 × 10⁶ years. We can calculate "k" using the following expression.
k = ln2/ t1/2 = ln2 / 703 × 10⁶ y = 9.86 × 10⁻¹⁰ y⁻¹
Step 2: Calculate the time elapsed (t) so that the final amount ([U]) is 23.0% of the initial amount ([U]₀)
For first order kinetics, we will use the following expression.
ln ([U]/[U]₀) = -k × t
ln (0.230[U]₀/[U]₀) = -9.86 × 10⁻¹⁰ y⁻¹ × t
ln 0.230 = -9.86 × 10⁻¹⁰ y⁻¹ × t
t = 1.49 × 10⁹ y
Describe why corrosion is a natural process
Answer :
Answer :because it happens due to moisture and oxygenAn experiment was performed under identical conditions as yours. The absorbance of the penny solution was recorded as 0.219 absorbance units. A calibration plot of absorbance vs. concentration of Cu(II) (M) yielded the following trendline equation:
y= 11.589x - 0.0002
Required:
What is the concentration (mol/L) of the penny solution?
Answer:
Concentration C = 0.0189 mol/L
Explanation:
From the given information:
Let consider the formula used in calculating the concentration according to Beer's law:
[tex]\mathtt{A =\varepsilon \times L \times C}[/tex] --- (1)
here;
A = absorbance
ε = coefficient of molar absorptivity
L = path length
C = concentration (mol/L)
Also, from Beer law plot:
y = mx+b
where,
y represent absorbance A
b represents intercept
m represents the coefficient of molar absorptivity ε
and x represents the concentration(C).
replacing the substituted entities
A = ε × C + b ---- (2)
Making the concentration the subject of the above formula:
[tex]C = \dfrac{A-b}{\varepsilon}[/tex]----(3)
From y = 11.589x - 0.0002
A = 11.589 *C - 0.0002
Given that:
A = 0.219
∴
0.219 = 11.589 *C - 0.0002
0.219 + 0.0002 = 11.589 *C
C = 0.2192/11.589
C = 0.0189 mol/L
A student measures her computer keyboard with a meter stick and finds that it has a width of 47.35 cm. Which statement about this measurement is true?
PLZZZZ HELP
A.) All the numbers are certain
B.) The 4 is uncertain
C.) The 5 is somewhat uncertain
D.) The 5 is certain
Boiling point-methanol (65.0) 66.8c.Boiling point-unknown (record from video)——-c
Identify of unknown:
Possibilities are:Mathanol65.0c;Ethanol 78.5c; Acetone 56.0C
Which of the following is NOT true about soil? *
examples of isotones
Answer:
Examples of isotones include carbon-12, nitrogen-13 and oxygen-14. These atoms all have six neutrons and six, seven and eight protons respectively. A mnemonic that can be used to differentiate isotones from isotopes and isobars is as follows: same Z (number of protons) = isotopes.
n a combination redox reaction, two or more ____________ , at least one of which is a(n) ____________ , form a(n) ____________ . General Reaction: ____________ In a decomposition redox reaction, a(n) ____________ forms two or more ____________ , at least one of which is a(n) ____________ . General Reaction: ____________ In double-displacement (metathesis) reactions, such as precipitation and acid-base reactions, ____________ of two ____________ exchange places; these reactions ____________ redox processes.General Reaction: ____________ In solution, single-displacement reactions occur when a(n) ____________ of one ____________ displaces the ____________ of another. Since one of the ____________ is a(n) ____________ , a
Answer:
In a combination redox reaction, two or more reactants, at least one of which is a(n) element, form a(n) compound. General Reaction: X + Y > Z
In a decomposition redox reaction, a(n) compound forms two or more products, at least one of which is a(n) element. General Reaction: Z>X+Y
In double-displacement (metathesis) reactions, such as precipitation and acid-base reactions, atoms (or ions) of two compounds exchange places; these reactions are not redox processes. General Reaction: AB+CD>AD+CB
In solution, single-displacement reactions occur when a(n) atom of one element displaces the atom of another. Since one of the reactants is a(n) element, all single-displacement reactions are redox processes. General Reaction: X+YZ>XY+Z
Explanation:
In a combination redox reaction, two or more reactants, at least one of which is a(n) element, form a(n) compound.
General Reaction: X + Y > Z
In the reaction scheme above, X combines with Y to give Z as a product.
In a decomposition redox reaction, a(n) compound forms two or more products, at least one of which is a(n) element.
General Reaction: Z>X+Y
In the reaction scheme above, Z decomposes to X and Y
In double-displacement (metathesis) reactions, such as precipitation and acid-base reactions, atoms (or ions) of two compounds exchange places; these reactions are not redox processes since there are no changes occurring in the oxidation number of the atoms (or ions) involved.
General Reaction: AB+CD>AD+CB
In the reaction scheme above, B and D exchange places in their respective compounds
In solution, single-displacement reactions occur when a(n) atom of one element displaces the atom of another. This type of reaction is due to the difference in the reactivities of the elements. The more reactive atom of one element displaces the least reactive atom of another element from its solution.
Since one of the reactants is a(n) element, all single-displacement reactions are redox processes.
General Reaction: X+YZ>XY+Z
In the reaction scheme above, X displaces Z from the compound YZ.
PLZZZ HELPPPPPPPPPPPPPPPP
Fabric A is used to rub a wooden rod. A second piece of Fabric A is used to rub an ebonite rod. It is observed that the wooden rod and the ebonite rod attract one another. What can you say about the position of Fabric A in the electrostatic series in relation to wood and ebonite?
Fabric A is likely to be a material that has a moderate tendency to gain electrons when in contact with other materials and is lower in the electrostatic series than ebonite but higher than wood.
What is electrostatic series?The electrostatic series is a list of materials ranked in order of their tendency to gain or lose electrons when in contact with another material.
Materials higher in the series tend to lose electrons more readily and become positively charged, while materials lower in the series tend to gain electrons more readily and become negatively charged.
Ebonite is a synthetic polymer that is known to become negatively charged when rubbed, and it is typically placed near the top of the electrostatic series.
Wood, on the other hand, is a poor conductor of electricity and does not readily become charged when rubbed. Based on these facts, we can infer that Fabric A is lower in the electrostatic series than ebonite, but higher than wood.
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What are the main modifications of John Dalton's atomic theory
Match each term with the best description.
a. The electrode where oxidation occurs
b. A device that produces electricity
c. The connection between two half-cells
d. The electrode where reduction occurs
e. A device that consumes electricity
f. A device that utilizes redox reactions to either consume or produce electricity
1. Anode
2. Cathode
3. Electrolytic cell
4. Electrochemical
5. Galvanic cell
6. Salt bridge
Answer:
Match each term with the best description.
a. The electrode where oxidation occurs: Anode
b. A device that produces electricity: Galvanic cell
c. The connection between two half-cells: salt bridge
d. The electrode where reduction occurs: Cathode
e. A device that consumes electricity: Electrolytic cell
f. A device that utilizes redox reactions to either consume or produce electricity: Electrochemical cell.
Explanation:
a.The electrode where oxidation occurs is called the anode.
Oxidation is losing of electrons.
b. Galvanic cell produces electricity by using redox chemical reaction.
It is also called a voltaic cell or electrochemical cell.
c. The connection between two cells is called a salt bridge.
It will not allow the solutions to diffuse with each other.
It maintains electrical neutrality.
d. The electrode where reduction occurs: Cathode
Reduction means the gaining of electrons.
e. Electrolytic cell is the one that consumes electricity and then produces a chemical change.
f. A device that utilizes redox reactions to either consume or produce electricity: Electrochemical cell.
Based on your knowledge of factors affecting the rate of reaction, why is there a danger of explosions in places such as flour mills and coal mines where there are large quantities of powdered, combustible materials?
Answer:
See Explanation
Explanation:
Rate of reaction refers to how quickly or slowly a reaction proceeds. The rate of reaction depends on certain factors.
Two among the factors that affect the rate of reaction are the concentration of reactants and the surface area of reactants.
The more the concentration of reactants, the faster the rate of reactants because there is a high possibility of collision between reactants. Also, the higher the surface area of reactants, the greater the rate of reaction.
In flour mills and coal mines where there is a large amount (concentration) of combustible materials and the particles are powdered (high surface area), there is a greater risk of explosion due to a high rate of reaction owing to a combination of the two factors discussed above.
A student collecting CaCO3 produced by the reaction of Na2CO3(aq) and CaCl2(aq) obtains a percent yield of 81%. Choose all of the following observations that could explain the low yield.
a. The combined reactants were not stirred before filtering the precipitate.
b. The student did not completely dry the precipitate before weighing it.
c. The precipitate was not washed prior to drying.
d. A rubber policeman was not used to scrape precipitate from the beaker.
e. The filter paper was not wetted with water prior to filtering the precipitate.
Answer:
a, d and e. are true.
Explanation:
The reaction that occurs is:
Na2CO3(aq) + CaCl2(aq) → CaCO3(s) + 2NaCl
In ideal conditions, the percent yield of the reaction must be 100%. All explanations about why the student could not collect all precipitate are right:
a. The combined reactants were not stirred before filtering the precipitate. Not stirring could not promote all the reaction. TRUE.
b. The student did not completely dry the precipitate before weighing it. If the student don't dry the precipitate, the mass of precipitate must be higher producing a percent yield > 100%. FALSE.
c. The precipitate was not washed prior to drying. Produce more mass. FALSE.
d. A rubber policeman was not used to scrape precipitate from the beaker. If the student doesn't collect all the precipitate the percent yield could be < 100%.. TRUE.
e. The filter paper was not wetted with water prior to filtering the precipitate. TRUE. If you don't wet the filter paper you can lose a part of precipitate from the walls of this one.
How is the atomic mass of an element calculated?
Answer:
Mass number (A) is the number of nucleons (proton and neutron) present in a atom.
Explanation:
electrons don't cout since they are thousandth's of the mass of protons or neutrons
Nuclear reactions take place inside the nucleus of the atom. Which of the following does NOT represent an everyday example of a nuclear reaction?
Conversion of carbon dioxide and water in photosynthesis
Hydrogen atoms fused together in the Sun
Loss of protons and electrons in plutonium-240 decay
Energy produced by the Sun that is transferred to Earth
Answer:
Loss of protons and electrons in plutonium 240 decay is not an example of an everyday reaction
2) If the density of chloroform is 1.48 g/mL, what is the volume of 541 g of chloroform?
Answer:
V = 365.54 mL
Explanation:
Given that,
The density of chloroform, d = 1.48 g/mL
The mass of chloroform, m = 541 g
We need to find the volume of chloroform.
We know that,
Density = mass/volume
So,
[tex]V=\dfrac{m}{d}\\\\V=\dfrac{541\ g}{1.48\ g/mL}\\\\=365.54\ mL[/tex]
So, the volume of chloroform is 365.54 mL.
A weak acid is titrated with 0.1236 M NaOH. From the titration curve you determine that the equivalence point occurs after exactly 12.42 mL of NaOH have been added. What is the volume of NaOH at the half-equivalence point (a.k.a. the midpoint)
Answer: The volume of NaOH required at the half-equivalence point is 6.21 mL
Explanation:
The chemical equation for the reaction of a weak acid with NaOH follows:
[tex]HA+ NaOH\rightarrow NaA+H_2O[/tex]
From the equation, we can say that NaOH and weak acid is present in a 1 : 1 ratio.
We are given:
Volume of NaOH required at equivalence point = 12.42 mL
The volume of NaOH required at half-equivalence point will be = [tex]\frac{12.42mL}{2}=6.21mL[/tex]
Hence, the volume of NaOH required at the half-equivalence point is 6.21 mL
The volume of NaOH at the half-equivalence point is 6.21 mL
What is equivalence point?The equivalence point is the point at which equal amount of the acid and base have reacted.
How to determine the half-equivalence pointVolume at equivalence point = 12.42 mLVolume at half-equivalence point =?Half equivalence point = Equivalence point / 2
Half equivalence point = 12.42 / 2
Half equivalence point = 6.21 mL
Therefore, we can conclude that the volume of NaOH at the half-equivalence point is 6.21 mL.
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The half life for the radioactive decay of potassium-40 to argon-40 is 1.26×109 years. Suppose nuclear chemical analysis shows that there is 0.359 mmol of argon-40 for every 1.000mmol of potassium-40 in a sample of rock. Calculate the age of the rock.
Answer:
2.42x10⁹ years is the age of the rock
Explanation:
The decay of an isotope follows the equation:
Ln[A] = -kt + Ln[A]₀
Where [A] is amount of isotope after time t, k is decay constant and [A]₀ is the initial amount of the isotope
To find decay constant from half-life:
k = ln2 / half-life
k = ln2 / 1.26x10⁹years
k = 5.501x10⁻¹⁰ years⁻¹
As in the reaction, K-40 produce Ar-40:
[A] = 0.359mmol
[A]₀ = 0.359mmol + 1.000mmol = 1.359mmol
Replacing:
Ln[0.359mmol] = -5.501x10⁻¹⁰ years⁻¹t + Ln[1.359mmol]
-1.3312 = -5.501x10⁻¹⁰ years⁻¹t
t = 2.42x10⁹ years is the age of the rock
A steel with a critical fracture toughness of 150 MPa.m1/2 has a yield strength of 1500 MPa. If fracture were to take place at the yield stress, answer the following questions.
Surface crack size at yielding leading to failure is:_____________.
a. 0.497 cm
b. 0.994 cm
c. 0.32 cm
Answer:
c.
Explanation:
From the given information:
Critical fracture toughness [tex]K_{IC}[/tex] = 150 MPa.[tex]m ^{1/2}[/tex]
yield strength [tex]\sigma[/tex] = 1500 MPa
surface crack size [tex]a_c[/tex] = ???
The formula for the fracture toughness is can be expressed as:
[tex]K_{IC}= \sigma \sqrt{\pi a_c}[/tex]
replacing our values to solve for the surface crack size, we have:
[tex]150= 1500 \sqrt{\pi a_c}[/tex]
[tex]\dfrac{150}{ 1500} = \sqrt{\pi a_c}[/tex]
[tex]\dfrac{0.1}{1.77} = \sqrt{ a_c}[/tex]
[tex]a_c[/tex] = 0.0564²
[tex]a_c[/tex] = 0.0032 m
[tex]a_c[/tex] = 0.32 cm
An organelle that is not found in this illustration of a cell would be
A. the cell wall
B. chromosome
C. mitochondria
D. the cell membrane
Answer:
The answer is cell wall
Explanation:
Because it is
Question 11
1 pts
A solution is formed by dissolving 45 grams of NH4Cl in
100 grams of H20 at 70°C. Which statement correctly
describes this solution?
O NH4Cl is the solute, and the solution is saturated.
O NH4Cl is the solute, and the solution is unsaturated.
o NH4Cl is the solvent, and the solution is unsaturated.
O NH4Cl is the solvent, and the solution is saturated.
< Previous
Answer:
NH4Cl is the solute, and the solution is unsaturated.
Explanation:
To create a saturated solution of ammonium chloride at 70°C, we need to dissolve 62 g of ammonium chloride in 100 g of water.
The question tells us that 45 grams of NH4Cl was dissolved in 100 grams of H20 at 70°C. This creates an unsaturated solution since the amount of solute present is less than the amount of solute that the NH4Cl solution can normally hold at 70°C.
Hence, NH4Cl is the solute, and the solution is unsaturated.
Spell out the full name of the compound.
Submit
Help plz
Explanation:
A=Butan-2-one
B=Pentan-3-one
Chemistry Grade 11: Hi, I don't know what this is, please help?
CALCULATING % YIELD STEPS:
1.
2.
3.
4.
Answer:
1. Write the balanced chemical equation for the reaction
2. Identify all important information provided in the word problems or data table.
3. Solve for the theoretical yield of the reaction, following all the steps of a stoichiometry calculation organizer. Use two calculations if both reactants are provided.
4. Use the percent yield equation to calculate the percent yield of the reaction.
Explanation:
its comes right from the 5.06 lesson
The acid dissociation constant, Ka, of HNO3 is 4.0 x104. What does the ka
value indicate about this compound?
A. HNO3 is neither an acid nor a base,
B. HNO3 is a strong acid.
C. HNO3 is a weak acid
D. HNO3 is a strong base.
Answer:
i thing its b
Explanation:
The acid dissociation constant (Ka) is a measure of the strength of an acid in solution. In HNO₃ (nitric acid), the given Ka value is 4.0 x 10⁴. It represents the equilibrium constant for the dissociation reaction of an acid in water. Therefore, option B is correct.
The dissociation constant often denoted as Kd, is a measure of the strength of the interaction between a ligand and a receptor or between a substrate and an enzyme.
A high Ka value indicates a strong acid, while a low Ka value indicates a weak acid. In this case, the Ka value of 4.0 x 10⁴ for HNO₃ is relatively high.
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A 0.15 M solution of BaCl2 contains: Group of answer choices 0.30 M Ba2 ions and 0.30 M Cl- ions. 0.15 M Ba2 ions and 0.15 M Cl- ions. 0.30 M Ba2 ions and 0.15 M Cl- ions. 0.15 M Ba2 ions and 0.30 M Cl- ions. none of the above
Answer:
0.15 M Ba⁺² ions and 0.30 M Cl⁻ ions
Explanation:
The dissociaton of barium chloride is as follows:
BaCl₂ → Ba²⁺ + 2Cl⁻
By observing the stoichiometric coefficients, we can tell that the number of moles of Ba²⁺ is the same as the number of moles of BaCl₂, while the number of moles of Cl⁻ is the double of that.
During a reaction in an aqueous solution, the concentration of bactants
decreases and the amount of products increases. How do these changes in
concentration affect the reaction rate?
A. The reaction rate decreases.
B. The reaction rate varies unpredictably.
C. The reaction rate increases.
D. The reaction rate stays the same.
Answer:
my define it will be turst me is c
Calculate the pressure exerted by 40 g of oxygen enclosed in a 1litre flask at 25°C. (0=16) (3 Marks)
Answer:
I don't know sorry siso
Explanation:
I don't know
Compare the solubility of silver chloride in each of the following aqueous solutions:
a. 0.10 M AgNO3 More soluble than in pure water.
b. 0.10 M NaCI Similar solubility as in pure water
c. 0.10 M KNO3 Less soluble than in pure water.
d. 0.10 M NH4CH3COO
Answer:
Compare the solubility of silver chloride in each of the following aqueous solutions:
a. 0.10 M AgNO3 More soluble than in pure water.
b. 0.10 M NaCI Similar solubility as in pure water
c. 0.10 M KNO3 Less soluble than in pure water.
d. 0.10 M NH4CH3COO
Explanation:
This is based on common ion effect.
According to common ion effect, the solubility of a sparingly soluble salt decreases in a solution containing common ion to it.
The solubility of AgCl(s) is shown below:
[tex]AgCl(s) <=> Ag^{+}(aq)+Cl^-(aq)[/tex]
So, when it is placed in:
a. 0.10 M AgNO3
Due to common ion effect Ag+, its solubility is less in this solution than in pure water.
b. 0.10 M NaCI :
Due to common ion effect Cl-, its solubility is less in this solution than in pure water.
c. 0.10 M KNO3 :
In this solution there is no presence of common ion.
So, the solubility of AgCl in this solution is similar to that of pure water.
d. 0.10 M NH4CH3COO:
In this solution, AgCl forms a precipitate.
So, the solubility of AgCl is more in this solution compared to pure water.
Using Hess’s law, what is the standard enthalpy of formation of manganese (II) oxide, MnO(s)?
With the help of hess's law:
ΔHf(MnO)=−248.9 kJ−12(272.0) kJ=−384.9 kJ(per mole) Δ H f ( M n O ) = − 248.9 k J − 1 2 ( 272.0 ) k J = − 384.9 k J ( p e r m o l e )
What is Hess's law?Hess's law of constant heat summation, also known simply as Hess' law, is a relationship in physical chemistry named after Germain Hess, a Swiss-born Russian chemist and physician who published it in 1840.
Moreover, hess's Law of Constant Heat Summation (or just Hess's Law) states that regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes.
Therefore, hess' law is based on the state function character of enthalpy and the first law of thermodynamics. Energy (enthalpy) of a system (molecule) is a state function.
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The products in a decomposition reaction _____. are compounds can be elements or compounds are elements include an element and a compound
Answer:
compounds are elements include an element and a compound
Explanation:
elements in the decomposition reaction is the substance that cannot be separated into simpler substances. Compounds, technically act as a reactant in the decomposition reaction, but since the reaction breakdown one substance into two or more, sometimes it exists in the product
