Answer:
7.5 sec.
Explanation:
A = A₀e⁻^kt => k = ln(A/A₀)/-t => ln(6.25/100)/-30s = 0.0924 s⁻¹
k·t₀.₅=0.693 => t₀.₅=0.693/k = (0.693/0.0924)s = 7.5 s
The half life of an isotope can be calculated from the decay constant of . The half life of H-2 if only 6.25 % remains after 30 seconds is 17.25 seconds.
What is half life?Unstable radioactive isotopes undergo nuclear decay by emitting charged particles such as alpha particles or beta particles. The nuclear decay process results in a stable isotope or new atom.
It is given that the final amount of the isotope is 6.25% and and the time taken for the decay is 30 seconds. Let the initial amount be 100%.
The decay constant k can be calculated as follows:
k = 1/t log (100/6.25)
= 1/30 s log 16
= 0.0401 s⁻¹
Now, the half life time can be determined as below:
half life t1/2 = 0.693 /k
= 0.693 /0.0401 s⁻¹
= 17.25 seconds.
Hence, the half life time of the given H-2 isotope is 17.25 seconds.
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In the reaction 2 Na(s) + F2(g) --> 2NaF (s), Given 12.5 g of fluorine with enough sodium, what mass of sodium fluoride forms?
Answer:
the mass of sodium fluoride is 15
Explanation:
One mole of F₂ or 38 g produces two moles or 84 g of NaF. Hence, 12.5 g of F₂ will produce 27.6 g of NaF.
What is sodium fluoride?Sodium fluoride is an ionic compound formed by the reaction of sodium metal and fluorine atom . Sodium metal loses one electron to fluorine and thus two moles of sodium and fluorine molecule produces 2 moles of NaF.
The molar mass of F₂ is 38 g. The molar mass of NaF is 42 g/mol. Thus mass of two moles of NaF is 84 grams. As per the balanced reaction, one mole or 38 g of F₂ produces two moles or 84 g of NaF. Thus mass of NaF is calculated as follows:
Mass of NaF = (12.5 g × 84 g) /38 g.
= 27.6 g.
Therefore, the mass of NaF produced by 12.5 g of F₂ in this reaction is 27.6 grams.
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Using the model of the Periodic Table, which two elements pictured have similar chemical properties?
Answer:
C) 1 and 3
Explanation:
A period in the periodic table is a row of chemical elements. All elements in a row have the same number of electron shells. ... Arranged this way, groups of elements in the same column have similar chemical and physical properties, reflecting the periodic law.
Is it true barium ion Games to electrons to make its valence shell full
Answer:
It is false
Explanation:
Barium does not gain electrons to make its valences shell full. In truth, Barium loses electrons to attain a complete octet configuration of its shell.
This is because, barium is electropositive and not electronegative.
As with most metals, barium will prefer to lose two electrons when forming bonds. The loss of two electrons makes it isoelectronic with the corresponding noble gas.Calculate the volume in liters of 0.558 M KOH necessary to titrate 0.016 moles of hydrochloric acid, HCl, to a phenolphthalein end-point.
Answer:
Explanation:
Let the volume required be v litre .
moles of KOH in v litre of .558 M of KOH = v x .558 moles
1 mole of KOH reacts with 1 mole of HCl
v x .558 moles of KOH reacts with v x .558 mole of HCl
v x .558 = .016
v = .016 / .558
= .02867 litre
= 28.67 mL .
Balance chemical equation CuS(s)+HCl(aq)=CuCl2(aq)+ H2S(g)
Answer:
CuS(s) + 2HCl(aq) —> CuCl2(aq) + H2S(g)
Explanation:
CuS(s) + HCl(aq) —> CuCl2(aq) + H2S(g)
The above equation can be balance by by doing the following:
CuS(s) + HCl(aq) —> CuCl2(aq) + H2S(g)
There are 2 atoms of H on the right side and 1 atom on the left side. It can be balance by putting 2 in front of HCl as shown below:
CuS(s) + 2HCl(aq) —> CuCl2(aq) + H2S(g)
Now the equation is balanced since the number of atoms present in the elements are the same on both side of the equation i.e
Reactant:
Cu = 1
S = 1
H = 2
Cl = 2
Product:
Cu = 1
S = 1
H = 2
Cl = 2
Therefore, the balanced equation is:
CuS(s) + 2HCl(aq) —> CuCl2(aq) + H2S(g)
The natural isotopes of Iron are Fe-55 and Fe-56. If the average atomic mass is 55.85, what are
the percent abundances of each isotope?
Answer:
15%
85%
Explanation:
Let the natural abundance of Fe-55 = y
the natural abundance of Fe - 56 = 1-y
Average atomic mass = 55.85
Unknown:
Percent abundances of each isotope = ?
Solution;
The average atomic mass of a substance is given as;
Average atomic mass = (mass x abundance)Fe - 55 + (mass x abundance)Fe - 56
Now insert the parameters and solve;
55.85 = (55 x y) + [56 x(1-y)]
55.85 = 55y + 56 - 56y
55.85 = -y + 56
55.85 - 56 = -y
-0.15 = -y
y = 0.15
1-y = 1 - 0.15 = 0.85
Percentage abundance;
Fe - 55 = 0.15 x 100 = 15%
Fe - 56 = 0.85 x 100 = 85%
HELP!!!!!!!!!!’nQuestion 3. Can you please explain how to get the answer? Starting with acetylene, devise a scheme to prepare 1-chloroheptanol
. There is more
than one way to complete this synthesis. It can be completed in as few as three reactions. You
can use any alkyl halides as needed as sources of carbon atoms.
Answer:
See explanation and image attached
Explanation:
Let us consider the mechanism attached to this answer. This is only one of the ways of synthesizing the required product.
The starting material is acetylene. This is reacted with sodamide in ammonia alongside methyl iodide. The process is repeated again, this time using butyl iodide. The alkyne is now reduced using hydrogen.
The alkane formed may now be chlorinated in the presence of light using the chlorine molecule. A mixture of alkyl halides are obtained.
❗️❗️i need help with 10 pages of 11th grade chemistry questions. they are mostly mutiple choice. i really need this done I WILL PAY MONEY
Answer:
What are the pages on? Like what topic?
Explanation:
An element has a half-life of 5.0 days. How many days would
pass before only 1/8th of the original amount of a sample of this
element remained?
Answer:
15 days
Explanation:
Given half-life = 5 days => k = 0.693/half-life = 0.693/5 days⁻¹
A = A₀e^-k·t => t = ln(A/A₀) / -k = ln(1/8) / -0.1386 days⁻¹ = 15 days
The element with half life of 5 days have the decay constant of 0.1386 dy⁻¹ will take 15 days to decay to its 1/8th part of initial amount.
What is half life ?Heavy unstable radioactive isotopes undergo nuclear decay by the emission of charged particles. Nuclear decay is a first order reaction.
Thus, the decay constant k = 1/t ln W0/Wt
where t is the time of decay, W0 be the initial amount and Wt be the amount after time t.
The half life of the element = 5 days.
decay constant = 0.693/t1/2
k = 0.693/5 days = 0.1386 days⁻¹.
The time taken to decay to 1/8th of its original amount is calculated as follows:
t = 1/k ln Wo/(Wo/8 )
= ln 8/0.1386 days⁻¹
= 15 days.
Therefore, the days before the element decay to its 1/8th of original amount is 15 days.
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What is the oxidation number of vanadium in V₂O₅?
Answer:
+4
Explanation:
Treatment of the ammonium metavanadate with hot hydrochloric acid partly reduces the vanadium to the +4 oxidation state in the form of the VO2+ ion.
In vanadium oxide we increase both sides by 4. And we discover that x is equal to five. The vanadium's oxidation number is + 5.
What is oxidation ?
Loss of electron is called as oxidation. and addition of oxygen molecule is also the oxidation.
When an object comes into touch with oxygen or another oxidizer, a chemical reaction occurs. Rust and the brown color of a sliced apple are both examples of oxidation.
Antoine Lavoisier used the term "oxidation" to describe the reaction of a material with oxygen. The meaning was later expanded to cover additional reactions in which electrons are lost, regardless of whether oxygen was present, after it was realized that the substance loses electrons when it is oxidized.
Thus, the oxidation number of vanadium in V₂O₅ is + 5.
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If you add 90 mL of 0.15M stock solution, to 10 mL of water, what is the new concentration?
0,15 moles of NaOH-------in------------1000ml
x moles of NaOH------------in--------100ml
x = 0,015 moles of NaOH
final volume = 150ml
0,015 moles of NaOH---in-------150ml
x moles of NaOH--------------in-----1000ml
x = 0,1 moles of NaOH
answer: 0,1mol/dm³ (molarity)
A sample of 0.300 moles of nitrogen occupies 0.600 L. Under the same conditions, what number of moles occupies 1.200L
Answer:
0.600 moles has volume 1.200L
Explanation:
The volume is numerically double the moles
0.600 mol occupies 1.200L
Mathematically:
V1/moles1 = V2/moles2
1.200L / moles1 = 0.600L/ 0.300mol
Moles 0.600L = 1.200L * 0.300mol
Moles = 1.2000L *0.300 mol / 0.600L
moles = 0.600 moles.
If an object that stands 3 centimeters high is placed 12 centimeters in front of a plane mirror, how far from the mirror is the image located? Explain your reasoning.
Answer:
the mirror is 12 cm away from the image
Explanation:
; the image will be virtual and it will form at 12 cm distance behind the mirror.
Consider separate solutions of NaOH and KClmade by dissolving 100.0 g of each solute in 250.0 mL of solution. Calculate the concentration of each solution in units of molarity.
Answer:
Explanation:
MW of NaOH = 40 g/mol
MW of KCl = 74.55 g/mp;
250 mL = .25 L
100g NaOH / 40 g = 25 mol
100g KCl/ 74.55g = 1.34 mol
Molarity of NaOH: 25/.25 = 100M
Molarity of KCl: 1.34/.25 = 5.36 M
100M is the concentration of NaOH.
5.36 M is the concentration of KCl.
Define the molarity of a solution.Molarity (M) is the amount of a substance in a certain volume of solution. Molarity is defined as the moles of a solute per litres of a solution.
The scientific noun molarity describes the concentration of a substance as measured by the number of moles divided by the volume of the solution in litres.
[tex]Molality = \frac{Moles \;solute}{Volume\; of \;the \;solution \;in \;litres}[/tex]
Molecular weight of NaOH = 40 g/mol
Molecular weight of KCl = 74.55 g/mp;
250 mL = .25 L
100g NaOH ÷ 40 g = 25 mol
100g KCl ÷ 74.55g = 1.34 mol
Molarity of NaOH: 25 ÷ .25 = 100M
Molarity of KCl: 1.34 ÷ .25 = 5.36 M
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In the combustion reaction 2C2H6 + 702 → 4C02 + 6H20, ethane gas reacts with oxygen to
produce carbon dioxide and steam. If 18.6 grams of C2H6 reacts with O2, how many moles of
steam does it produce?
Answer:
1.86moles
Explanation:
Given chemical reaction:
2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O
Mass of C₂H₆ = 18.6g
Unknown:
Number of moles of steam produced = ?
Solution:
2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O
We have checked and the equation is balanced.
Now, find the number of moles of C₂H₆ from the given mass;
Number of moles = [tex]\frac{mass}{molar mass}[/tex]
Molar mass of C₂H₆ = 2(12) + 6(1) = 30g/mol
Number of moles = [tex]\frac{18.6}{30}[/tex] = 0.62moles
From the balanced reaction equation:
2 mole of C₂H₆ will produce 6 moles of steam
0.62 moles of C₂H₆ will therefore produce [tex]\frac{0.62 x 6}{2}[/tex] = 1.86moles
Helpppp pleaseeeeeee
Answer: c
Explanation:
The major reason why relative atomic mass of some elements is not a whole number the existence
Answer:
Because of the existence of isotopes.
Answer:
Because of the existence of isotopes.
Which one is being shown in this picture?
Answer:
B. REFRACTION.
Is shown in fig.
ANSWER ASAP GIVING BRAINLIEST!
A chemical reaction in a light stick causes it to give off a glowing green light. Explain why the reaction is endothermic or exothermic.
Answer:
Glow sticks give off light but not heat because energy is released, the glow stick reaction is an example of exergonic (energy-releasing) reaction. However, it is not an exothermic (heat-releasing) reaction because heat isn't released... endothermic reactions absorb heat.
Explanation:
*Hope this helps*
Which term refers to the loss of fertile soil from drying out?
erosion
desertification
depletion
overuse
Answer:
Desertification
Explanation:
I took the test
Desertification is the loss of fertile soil from drying out.
What is desertification?Desertification is the process where by the fertile soil is washed away and dry out because of overexposure and absence of trees to hold the soul together and drought.
Therefore, Desertification is the loss of fertile soil from drying out.
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Which statement best describes the relationship between the frequency and energy of light?
A) the lower the frequency the greater the energy of light. B) more information is needed since there is an additional term (h) in the equation relating frequency and energy. C) the higher the frequency the lower the energy of light. D) the higher the frequency the greater the energy of light.
Answer:
D) the higher the frequency the greater the energy of light.
Explanation:
Energy and frequency of light are directly connected. The higher the frequency ,the greater the energy of light.
As frequency increases, the energy of light also increases.
Frequency is the number of photons that passes through a point at a period of time. The more the the photons, the more energy light carries.Mathematically;
Energy = hf
h is planck's constant
f is the frequency.
The picture below shows a specific nuclear reaction occurring. What best describes the unlabeled particle shown at the bottom of the picture that is released during this reaction? *
a gas container with a volume of 271 mL contains 0.26 moles of gas. Gas is added to the container so that it now contains 0.80 mole of gas. what is the new volume in milliliters
Answer:
V₂ = 833.85 mL
Explanation:
Given data:
Initial volume V₁= 271 mL
Initial number of moles n₁= 0.26 mol
Final number of moles n₂= 0.80 mol
Final/new volume V₂ = ?
Solution:
V₁/n₁ = V₂/n₂
Now we will put the values in formula.
271 mL / 0.26 mol = V₂ / 0.80 mol
V₂ = 271 mL × 0.80 mol / 0.26 mol
V₂ = 216.8 mL.mol / 0.26 mol
V₂ = 833.85 mL
Rank the following salts in order of increasing lattice energy: lithium chloride, calcium oxide, aluminum oxide, sodium chloride, barium oxide.
Please explain! Thank you.
Answer:
barium oxide < calcium oxide< sodium chloride < lithium chloride < aluminum oxide
Explanation:
The lattice energy can be defined as the change in internal energy accompanying the formation of a single mole of an ionic solid from its gaseous constituents at 0 K.
The lattice energy depends on the relative sizes of cations and anions in the compound. The smaller the cations and anions, the greater the lattice energy.
If we look as the proposed order of increasing lattice energy of the compounds; barium oxide < calcium oxide< sodium chloride < lithium chloride < aluminum oxide, we will notice that it follows the order of decrease in the sizes of both the ions, Ba^2+ > Ca^2+ > Na+ >Li+ > Al^3+.
The smaller the ions involved, the greater the lattice energy as one can see from the order listed above.
Barium oxide < calcium oxide< sodium chloride < lithium chloride < aluminum oxide is the rank of salts in the increasing order of their lattice energy.
What is lattice energy?Lattice energy is define as the amount of internal energy required for the formation of one mole of ionic compound by its constitute ions.
Lattice energy is inversely proportional to the size of ions present in the ionic compound. In the given question order of size of ions are:
Ba²⁺ > Ca²⁺ > Na⁺ > Li⁺ > Al³⁺
From the above order it is clear that size of aluminum ion is smallest, so lattice energy for this ionic compound is more and sequence of salts in the increasing order of lattice energy is as follow:
barium oxide < calcium oxide< sodium chloride < lithium chloride < aluminum oxide
Hence, Aluminum oxide has highest lattice energy and barium oxide has minimum.
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What is the ionization charge for the elements found in Group II?
Answer: a + 2
Explanation: Alkali Earths or Group II has an ionization charge of a + 2. Alkali Metals have a ionization a + 1. Halogens or cold elements have a ionization of a +3.
What is the formula for Chromium (III) Bisulfite?
Answer:
Cr2(SO4)3
Explanation:
How does it feel like to drown
Answer:
when you drown your lungs fill up with water so it like severe pain that won't go away until your dead so it like drink milk through nose imagine that and you can't breath that is what it is like to drown
Explanation:
PLEASE HELPPPP! HOW DO I DO THIS???
1. Calculate the amount of heat released when a 225 g sample of gold cools from 86.0oC to 32.5oC. The specific heat of gold is 0.129 J/goC
2. A 19.6 g sample of a metal was heated to 61.67oC. When it was placed into 26.7 g of water in a constant pressure calorimeter, the temperature of the water rose from 25.00oC to 30.00oC. Determine the specific heat of the metal if the specific heat of H2O(liq) is 4.18 J/goC. Ignore any contribution from the container.
Answer:
1552.83J Released
Explanation:
1. mass/m=225
Initial temp:86C, final:32.5C
Changed Temp: 32.5-86= -53.5C
s=0.129 J/gC
Formula: q= m times s times changed Temp.
q=(225)(0.129)(-53.5)
q= -1552.83 J
q=1552.83 J Released
If an object is not moving, it has no
A. potential energy
B. kinetic energy
c. elastic energy
D. nuclear energy
Answer:
that answer is B
Explanation:
the answer is b luv
Answer:
b
Explanation:
Which equation shows a physical change?
A.Pb(NO3)2 (aq) + 2KI(aq) → 2KNO3(aq) + PbI2(s)
B. HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
C.2H2O(l) → 2H2(g) + O2(g)
D.H2O(g) → H2O(s)
Answer:
The correct option is D
Explanation:
A physical change is a change in which no new substance is formed and can be easily reversible.
Of the options provided, option D is correct because gaseous water (steam) can be converted to solid water (ice) through freezing and can be reversed by heating up the solid water. Thus, this process does not involve the formation of any new substance.
Note that the processes of freezing and heating described must pass through the liquid phase.