After three half-lives, 12.5% of the original radioactive parent isotope will remain.
To determine the remaining amount of a radioactive parent isotope after a given number of half-lives, you need to understand the concept of radioactive decay.
A radioactive isotope undergoes decay, reducing its quantity over a set period known as a half-life.
Each half-life represents the time it takes for half of the parent isotope to decay into a daughter isotope.
Explanation and Calculation:
1. Concept of Half-Life:
- A half-life is the time required for half of the radioactive parent isotope to decay.
2. Formula for Remaining Fraction:
- The fraction of the parent isotope remaining after n half-lives can be calculated using the formula:
[tex]\[ \left(\frac{1}{2}\right)^n \][/tex]
- Here, n is the number of half-lives.
3. Calculation for Three Half-Lives:
[tex]\text{After 1 half-life:} \\\\\left(\frac{1}{2}\right)^1 = \frac{1}{2} = 0.5 \text{ (50\% remains)}\\\text{After 2 half-lives:} \\\\\left(\frac{1}{2}\right)^2 = \frac{1}{4} = 0.25 \text{ (25\% remains)}\\\text{After 3 half-lives:} \\\\\left(\frac{1}{2}\right)^3 = \frac{1}{8} = 0.125 \text{ (12.5\% remains)}[/tex]
Conclusion:
Thus, after three half-lives, only 12.5% of the original parent isotope remains. This is calculated using the formula [tex]\(\left(\frac{1}{2}\right)^n\)[/tex], where n is the number of half-lives.
An acid has an acid dissociation constant of 2.8x10^-9. What is the base dissociation constant of its conjugate base?
2.8x 10^-23
3.6x10^-6
2.8x10^5
3.6 x10^22
Answer: The correct answer is [tex]3.6\times 10^{-6}[/tex]
Explanation:
We are given:
Acid dissociation constant [tex](k_a)=2.8\times 10^{-9}[/tex]
Water dissociation constant [tex](k_w)=1\times 10^{-14}[/tex]
To calculate the base dissociation constant for the conjugate base, we use the equation:
[tex]k_w=k_a\times k_b[/tex]
where,
[tex]k_b[/tex] = base dissociation constant
Putting values in above equation, we get:
[tex]10^{-14}=2.8\times 10^-9}\times k_b\\\\k_b=3.6\times 10^{-6}[/tex]
Hence, the correct answer is [tex]3.6\times 10^{-6}[/tex]
Calculate the total percentage of oxygen in magnesium nitrate crystals, Mg(NO3)2.6H2O
If a large leak of refrigerant occurs such as from a filled cylinder in an enclosed area what action should be taken when no self-contained breathing apparatus is available?
If a large leak of refrigerant occurs in an enclosed area and no self-contained breathing apparatus is available, the immediate action should be to evacuate the area to fresh air, shut off the source of the leak if possible, and seek medical attention if experiencing symptoms.
Explanation:If a large leak of refrigerant occurs in an enclosed area and no self-contained breathing apparatus is available, there are several actions that should be taken to ensure safety:
Immediately evacuate the area to fresh air.If possible, shut off the source of the leak and prevent any additional release of refrigerant.Seek medical attention if experiencing any symptoms, such as difficulty breathing or irritation of the eyes, throat, or skin.It is important to prioritize personal safety and seek professional assistance when encountering such incidents.
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If 4.0 g of hydrogen and 10.0 g of oxygen are mixed according to the equation 2 h2 + o2 → 2 h2o, which is the limiting reagent?
Final answer:
To find the limiting reagent between hydrogen and oxygen, we convert their masses to moles and use the stoichiometry of the balanced chemical reaction 2 H2 + O2 → 2 H2O. Oxygen is the limiting reagent because there are not enough moles of O2 to fully react with the available moles of H2.
Explanation:
To determine the limiting reagent when 4.0 g of hydrogen (H2) and 10.0 g of oxygen (O2) are mixed to react according to the equation 2 H2 + O2 → 2 H2O, we need to perform mass-mole calculations for both reactants and compare the stoichiometry of the balanced equation.
First, convert the mass of each reactant to moles:
For H2: Molecular weight is approximately 2.02 g/mol. Thus, 4.0 g H2 ÷ 2.02 g/mol = 1.98 moles of H2.
For O2: Molecular weight is approximately 32.00 g/mol. Thus, 10.0 g O2 ÷ 32.00 g/mol = 0.3125 moles of O2.
According to the balanced equation, 2 moles of H2 react with 1 mole of O2. Therefore, to fully react with 1.98 moles of H2, we would need 0.99 moles of O2. However, we only have 0.3125 moles of O2, which is insufficient to react with all the H2. Therefore, O2 is the limiting reagent.
The central atom in the clf4 ion has ________ nonbonded electron pair(s) and ________ bonded electron pair(s) in its valence shell.
The central atom in the ClF4 ion has three nonbonded electron pairs and one bonded electron pair in its valence shell.
Explanation:The central atom in the ClF4 ion has three nonbonded electron pairs and one bonded electron pair in its valence shell. The Cl atom has a total of seven valence electrons and forms four covalent bonds with the four fluorine atoms. This leaves three lone pairs of electrons around the central Cl atom, which are not involved in bonding.
CH4(g) + H2O(g) mc004-1.jpg CO(g) + 3H2(g) What will happen to the equilibrium of this reaction if CO is added to the system?
Which graph is used to show change in a given variable when a second variable is changed?
Determine whether or not each mixture is a buffer. check all that apply. check all that apply. koh and nh3 hbr and nacl hcl and hbr hcho2 and nacho2
HCHO2 and NaCHO2, and CH3NH2 and CH3NH3Cl can make buffer solutions. HCl and NaCl, and NH3 and NaOH cannot make buffer solutions.
Explanation:1. HCHO2 is formic acid, a weak acid, while NaCHO2 is the salt made from the anion of the weak acid (the formate ion [CHO2]). The combination of these two solutes would make a buffer solution.
2. HCl is a strong acid, not a weak acid, so the combination of these two solutes would not make a buffer solution.
3. CH3NH2 is methylamine, which is like NH3 with one of its H atoms substituted with a CH3 group. Because it is not listed in Table 12.8.1, we can assume that it is a weak base. The compound CH3NH3Cl is a salt made from that weak base, so the combination of these two solutes would make a buffer solution.
4. NH3 is a weak base, but NaOH is a strong base. The combination of these two solutes would not make a buffer solution.
Type in the correct values to correctly represent the valence electron configuration of oxygen: AsB2pC
A =
B =
C =
Answer: A=2, B=2 and C=4
Explanation: Oxygen is the element with atomic number 8 and thus contains 8 electrons which are filled in order of increasing energy levels.
[tex]O:8:1s^22s^22p^4[/tex]
The valence electrons are electrons which are present in the valence shell i.e. the last shell. Thus the valence electrons of Oxygen are in shell 2 in which s orbital contains two electrons and the p orbital contains 4 electrons.
Thus A= 2, B=2 and C=4.
Answer:
The correct number of valance electrons in the electronic configuration of Oxygen is:
A=2, B=2, and C=4
Explanation:
The atomic number of oxygen is 8
The electronic configuration will be,
[tex]\rm O_8\rightarrow1s_2,2s_2,2p_4[/tex]
The electrons present in the outermost shell is called valence electrons.
Hence, in the second shell, the s-orbital contains 2 electrons and the p-orbital contains 4 electrons.
If all the electrons in the outermost shell are removed the first shell becomes a valance shell where 2 electrons are present in the s-orbital.
Therefore correct valence electron configuration is 2,2,4.
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How many moles of HNO3 are present if 2.50×10−2 mol of Ba(OH)2 was needed to neutralize the acid solution?
The number of moles of HNO3 present is 5.00×10^-2 mol.
Explanation:In the given neutralization reaction:
Ba(OH)2 (aq) + 2HNO3(aq) → Ba(NO3)2(aq) + 2H₂O(1)
It's clear that 2 moles of HNO3 are needed to neutralize 1 mole of Ba(OH)2. Therefore, if 2.50×10−2 mol of Ba(OH)2 was needed to neutralize the acid solution, we can calculate the number of moles of HNO3 as follows:
Number of moles of HNO3 = 2.50×10−2 x 2 = 5.00×10−2 mol
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In aqueous solution, globules of up to several thousand amphiphilic molecules arranged with the hydrophilic groups on the surface and the hydrophobic groups buried in the center are called _____.
Is aluminum homogeneous or heterogeneous?
For hydrogen, what is the wavelength of the photon emitted when an electron drops from a 4p orbital to a 2s orbital in a hydrogen atom?
soaps feel slippery on our hands because they dissolve the oil on our skin, decreasing friction. this is because soap contains
Soaps are made by the process saponification. Soaps contains long chain fatty acids and glycerol. The oily nature of soaps are due the presence of fatty acids.
What is saponification?Saponification is the process, making of soaps from glycerol and fatty acids. Therea are different types of soaps based on the ionic nature of the long chain fatty acids.
There are alkaline soaps in which the acidic chain possess a negatively charged group and acidic soaps are those bearing positively charged ions. The nature of sopas can be varied as per the use also.
Fatty acids are long chain hydrocarbons formed by the combination of simple hydrocarbons and they will reacts easily with alcohols forming esters of fatty acids that are soaps.
Hence, the presence of fatty acids make the soaps oily in nature and move gains friction in our hand.
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(6.21×10^3)(0.1050)
(Scientific Notation)
Which would least strongly attract electrons from other atoms in a compound? elements of group 1
elements of group 2
elements of group 15
elements of group 17
The elements with the least chances to attract electrons from the other atoms are group 1 elements. Thus option A is correct.
The elements attract or lose electrons in order to attain a stable configuration. The system has been based on the number of valence electrons in the atom.
The atom with the least electronegativity has the changes to give up the electrons, and the least chance to attract the electrons from the other atoms.
The group 1 elements have 1 valence electrons, and thus have the high chances to give the electron, with the least chances to attract electrons from the other compounds. Thus option A is correct.
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How does electronegativity cause the polarity in water and, ultimately, enable water to form hydrogen bonds between other water molecules?
Electronegativity in water creates partial charges, causing polarity. This polarity allows hydrogen bonding between water molecules, enhancing interactions.
In a water molecule (H₂O), oxygen is more electronegative than hydrogen. This means that oxygen attracts the shared electrons in the O-H bonds more strongly than hydrogen does.
As a result, the electrons spend more time closer to the oxygen atom, giving it a partial negative charge (δ−), while the hydrogen atoms acquire a partial positive charge (δ+). This uneven distribution of charge creates a dipole moment, making water a polar molecule.
The polarity of water molecules causes them to be attracted to each other. The partial positive charge of one water molecule is attracted to the partial negative charge of another, forming hydrogen bonds.
These bonds are relatively weak compared to covalent bonds but are crucial for water’s unique properties, such as its high boiling point and surface tension.
What process measures the amount of a solution of known concentration required to react with a measured amount of a solution of unknown concentration?
Titration is the process that measures the amount of a solution of known concentration required to react with a measured amount of a solution of unknown concentration.
Explanation:The process that measures the amount of a solution of known concentration required to react with a measured amount of a solution of unknown concentration is called titration. Titration is a quantitative chemical analysis method that involves measuring the volume of a reactant solution required to completely react with the analyte in a sample. The volume of the titrant solution is used to calculate the concentration of the analyte using the stoichiometry of the titration reaction.
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What is the oxidizing agent in galvanic cell?
Answer:
Anode
Explanation:
A p e x
The guy that said cathode was wrong :(
Calculate the energy difference for a transition in the paschen series for a transition from the higher energy shell n=4. express your answer to four significant figures and include the appropriate units.
The energy difference for a transition in the Paschen series from the higher energy shell n=4 is approximately 13.6 eV.
Explanation:The energy difference for a transition in the Paschen series can be calculated using the equation:
AE = E1 - E2 = 2.179 × 10-18 J
To express the answer in eV, we can use the conversion factor: 1 eV = 1.6022 × 10-19 J
Therefore, the energy difference for the transition in the Paschen series from the higher energy shell n=4 is approximately 13.6 eV.
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A certain radioactive element has a half-life of one hour. if you start with 1.0 gram of the element at noon, how much of the radioactive element will be left at 2 p.m.? 0.50 grams 0.25 grams 0.125 grams 0.0 grams
Answer:
The radioactive element will be left at 2 p.m. will be 0.25 g.
Explanation:
Half life of the radioactive element =[tex]t_{\frac{1}{2}}=1 hour[/tex]
Initial concentration of the radioactive element = [tex]N_o[/tex]=1.0 g
Time elapsed = 12:00 pm to 2:00 pm = 2 hours
Concentration of radioactive element left = N
[tex]\lambda =\frac{0.693}{t_{\frac{1}{2}}}=\frac{0.693}{1 hr}=0.693 hr^{-1}[/tex]
[tex]\log N=\log N_o-\frac{\lambda t}{2.303}[/tex]
Putting the given values in the above equation we get:
N = 0.25 gram
The radioactive element will be left at 2 p.m. will be 0.25 g.
Which of the following represents a hydrocarbon that contains one double bond somewhere in the carbon chain?
alkane
alkene
alkyne
substituted hydrocarbon
I know it's not C, alkyne
An alkene is a hydrocarbon with one or more carbon-carbon double covalent bonds, and is the correct answer to the question.
Explanation:An alkene is a hydrocarbon with one or more carbon-carbon double covalent bonds. Alkenes have the general formula CnH2n assuming non-cyclic structures. They can be represented by the formula RCH=CHR', where R and R' are any atoms or groups of atoms attached to the carbons.
An alkyne is a hydrocarbon with one or more carbon-carbon triple covalent bonds. Alkynes have the general formula CnH2n-2, and can be represented by the formula RC≡CR', where R and R' are any atoms or groups of atoms attached to the carbons.
Based on these definitions, the hydrocarbon that contains one double bond somewhere in the carbon chain is an alkene.
The correct symbol for the ion formed by nitrogen is:
The ion formed by nitrogen is N³⁻, also known as a nitride ion. In an ionic compound with aluminum, Al³⁺ forms the cation, and C⁴⁻ forms the anion called the carbide ion.
The correct symbol for the ion formed by nitrogen is N³⁻. Nitrogen, being in group 15 of the periodic table, is a nonmetal and thus forms negative ions, known as anions. A nitrogen atom will gain three electrons to achieve the electron configuration of neon, the next noble gas, resulting in the formation of a nitride ion with a 3- charge.
Rank these compounds by highest boiling point to lowest boiling point? Pentane, neopentane, isopentane
The compounds ranked by boiling point from highest to lowest are: Pentane > Isopentane > Neopentane.
The boiling point of a compound is influenced by its intermolecular forces.
Compounds with stronger intermolecular forces tend to have higher boiling points because more energy is required to overcome those forces and convert the substance from a liquid to a gas.
Generally, the strength of intermolecular forces increases with increasing molecular size and surface area.
Pentane is a linear hydrocarbon with five carbon atoms in a row. It has the highest boiling point among the three compounds because it has the greatest molecular size and surface area.
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How many subshells are there in the shell with n = 6?
Answer:
5 subshells
Explanation:
A technician has been given 250 ml of 15% acetic acid solution. the pharmacist has asked the tech to dilute the solution to 500 ml with sterile water and to label the solution. what percentage should appear on the label
The problem is about diluting a 15% acetic acid solution to a larger volume. After diluting the solution from 250 ml to 500 ml, the new percentage concentration of the acetic acid solution is 7.5%. Hence, the label should read 7.5% acetic acid.
Explanation:The problem you presented is a typical one in chemistry, which involves the concept of percentage concentration and dilutions. Initially, we have 250 ml of a 15% acetic acid solution. The amount of acetic acid in the solution is therefore 0.15 * 250 = 37.5 g.
The technician adds enough water to the solution to make the total volume 500 ml. However, the amount of acetic acid doesn't change; it remains 37.5g. To find the new percentage of the acetic acid solution, we take the total mass of the acetic acid (37.5g) and divide it by the total volume of the solution (500 ml), then multiply by 100% to get the percentage:
(37.5g / 500ml) * 100% = 7.5%.
So, the label on the solution should say 7.5% acetic acid.
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Chemistry balance skeleton reaction? Balance the following skeleton reactions and identify the oxidizing and reducing agents.; include states-of-matter please! 1.BH4‾(aq) + ClO3‾(aq) → H2BO3‾(aq) + Cl ‾(aq) [basic] 2.CrO42-(aq) + N2O(g) → Cr3+(aq) + NO(g) [acidic]
The given reactions are balanced, with the first reaction not requiring any adjustment and the second reaction being balanced as 2CrO42-(aq) + 3N2O(g) → 6Cr3+(aq) + 3NO(g). The oxiding agents are ClO3¯ and CrO42- for the first and second reactions, respectively. The reducing agents are BH4¯ and N2O for the first and second reactions, respectively.
Explanation:First, it's essential to know that during oxido-reduction reactions, one substance loses electrons (oxidized) and another gains them (reduced). We call the substance oxidized to be the reducing agent and the one reduced to be the oxidizing agent.
For the first reaction BH4¯(aq) + ClO3¯(aq) → H2BO3¯(aq) + Cl¯(aq), there aren't any charges or states of matter to be balanced. Analyzing the oxidation states, the B in BH4¯ goes from -3 to +3, showing it has been oxidized. Thus, BH4¯ is the reducing agent. ClO3¯ reduces to Cl¯, thus ClO3¯ is the oxidizing agent.
Moving on to the second reaction CrO42-(aq) + N2O(g) → Cr3+(aq) + NO(g), balance the equation first by adjusting coefficients to get 2CrO42-(aq) + 3N2O(g) → 6Cr3+(aq) + 3NO(g). This reaction is in an acidic solution, so it's important to note that hydroxide ions do not appear in half-reactions occurring in an acidic solution. SO, in this reaction too, Cr in CrO42- goes from +6 to +3, signifying reduction, making CrO42- the oxidizing agent. N in N2O goes from +1 to +2 which signifies oxidation, marking N2O as the reducing agent.
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The light intensity of a source is 100 candelas. The illuminance on a surface is 4 lux. How far is the surface from the source?
A. 7 meters
B. 6 meters
C. 4 meters
D. 5 meters
To find the luminous intensity this formula is used;
Luminous intensity = illuminance × [tex]radius ^{2}[/tex]
∴ Lv = Ev × [tex] r^{2}[/tex]
We know the luminous intensity is 100 candelas and the illuminance is 4 lux.
∴ 100 = 4 x [tex] r^{2}[/tex]
∴ 100/4 = [tex] r^{2}[/tex]
∴ 25 = [tex] r^{2}[/tex]
∴ r =√25 = 5 meters
Therefore, the surface will be at a distance of 5 meters from the source.
A reaction produces 0.819 moles of h2o. how many molecules are produced?
What is the Celsius temperature of 1 mole of a gas that has an average kinetic energy of 4,265 joules?
69°C
96°C
369°C
435°C
Answer:
Explanation:
Kinetic energy is the energy possessed by an object by virtue of its motion.
Average kinetic energy is defined as the average of the kinetic energies of all the particles present in a system. It is determined by the equation:
[tex]K=\frac{3nRT}{2}[/tex]
K= kinetic energy
n= number of moles
R= gas constant
T= temperature
[tex]4265J=\frac{3\times 1\times\times 8.314\times T}{2}[/tex]
[tex]T=342K[/tex]
[tex]tK=(t-273)^0C[/tex]
[tex]T=342K=(342-273)^0C=69^0C[/tex]
Thus temperature will be [tex]69^0C[/tex]