Answer:
Explanation:
a )
half life = 1600 years
50% in 1600 years
25% in next 1600 years
so 25% in total of 3200 years .
b )
disintegration constant = .693 / half life
= .693 / 1600
λ= 4.33 x 10⁻⁴ year⁻¹
m(t) = [tex]m_0e^{-\lambda t }[/tex]
m₀ is initial mass , λ = 4.33 x 10⁻⁴ year⁻¹
c )
m(t) after 3000 years , t = 3000
m(t) = [tex]m_0e^{-4.33\times10^{-4 }\times 3000 }[/tex]
= [tex]m_0e^{-1.3}[/tex]
= .2725 m₀
percentage of mass remaining = 27.25 %
25% radium-226 remain after 3200 years. 6.82 mg of sample remains after 3000 years. 15 mg of the sample will stay long about 1179. 19 years.
Half life of radium-226 = 1600 years
What is half-life?
half-life, in radioactivity, the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay.
Calculation of each part can be done as
a )
half-life = 1600 years
50% in 1600 years
25% in next 1600 years
so 25% in total of 3200 years .
b )
Let decay function is
[tex]m(t) = m_o e^{-kt} \ \ \ \ \ ...(i)\\[/tex]
where k is decay constant
At half life,
[tex]m(t) = \frac{m_o}{2},t= 1600\ years\\So,\ \frac{m_o}{2} = m_oe^{-k1600}\\\frac{1}{2} = e^{-k1600}\\[/tex]
applying log on both sides
[tex]ln \frac{1}{2} = lne^{-1600k}\\-0.693147 = -1600 k \\k =\frac {0.693147}{1600}\\k = 4.332\times10^{-4}\\[/tex]
substitute the value of k in equation (i)
[tex]m(t) = m_oe^{-4.332\times10^{-4t}}\\m(t) = 25e^{-0.0004332t}[/tex]
c) when t = 3000 years
[tex]m(t) = 25e^{-0.0004332t}[/tex]
[tex]m(3000) = 25e^{-0.0004332\times3000}[/tex]
remain sample after 3000 years = 6.82 mg
d) when m(t) = 15 mg
[tex]15 = 25e^{-0.0004332t}\\e^{-0.0004332 t} = \frac{15}{25}\\applying\ log\ on\ both\ side\\ln \ e^{-0.0004332t}=ln(\frac{15}{25)}\\-0.0004332t = -0.510825\\t=\frac{0.510825}{0.0004332}\\t= 1179.19 \ years[/tex]
Hence, this is the required answer.
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Ammonia, NH3 is a common base with Kb of 1.8 X 10-5. For a solution of 0.150 M NH3:
Write the equation for the ionization of ammonia in water.
List all species present in the solution AND determine the concentrations of each.
Determine the pH of this solution.
The concentrations : 0.15 M
pH=11.21
Further explanationThe ionization of ammonia in water :
NH₃+H₂O⇒NH₄OH
NH₃+H₂O⇒NH₄⁺ + OH⁻
The concentrations of all species present in the solution = 0.15 M
Kb=1.8 x 10⁻⁵
M=0.15
[tex]\tt [OH^-]=\sqrt{Kb.M}\\\\(OH^-]=\sqrt{1.8\times 10^{-5}\times 0.15}\\\\(OH^-]=\sqrt{2.7\times 10^{-6}}=1.64\times 10^{-3}[/tex]
[tex]\tt pOH=-log[OH^-]\\\\pOH=3-log~1.64=2.79\\\\pH=14-2.79=11.21[/tex]
Convert 85.02g to mg (1 mg=10^-3g)
Answer:
85,020 milligrams
Explanation:
Multiply the mass value by 1,000
Alcohol is a
Depressant
Muscle relaxer
Both
Alcohol is both a Depressant and a Muscle Relaxer. Therefore the answer would be both!
Hope this helps :)
PLS HELP!!!
What does it mean when there is a physical change?
A new substance has been formed.
Matter has changed on the molecular level.
Matter has changed from one substance into another.
Matter has changed size, shape or form.
Answer:
Physical Change. Physical changes are changes in which no bonds are broken or formed. This means that the same types of compounds or elements that were there at the beginning of the change are there at the end of the change.
Everything in outer space including stars, planets, and galaxies
O A. Solar System
B. Universe
OC. Galaxy
D. Biosphere
I
Answer:
Universe.
Explanation:
Biosphere is just a planet. Solar system contains planets and star. Galaxy holds multiple solar systems only. Universe hold everything, biospheres, solar systems, and galaxies. I hope this helps :D
Answer:
B.
Explanation:
A solar system is IN a galaxy. Its not A.
A Galaxy doesnt have other galaxies in it. Its not c
A biosphere is only referring to earth. its not D.
Therefore, it is B. A universe is everything in outer space including stars, planets, and galaxies.
PLS HURRY
What methods are you using to test this (or each) hypothesis?
Answer:
Fair test.
PLS GIVE BRAINLIEST
How many milliliters of 2.00 M H2SO4 will react with 28.0 g of NaOH?
Taking into account the reaction stoichiometry and the definition of molarity, 175 mL of 2 M H₂SO₄ will react with 28.0 g of NaOH.
Reaction stoichiometryIn first place, the balanced reaction is:
H₂SO₄ + 2 NaOH → Na₂SO₄ + 2 H₂O
By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:
H₂SO₄: 1 moleNaOH: 2 moles Na₂SO₄: 1 moleH₂O: 2 molesThe molar mass of the compounds is:
H₂SO₄: 98 g/moleNaOH: 40 g/moleNa₂SO₄: 142 g/moleH₂O: 18 g/moleThen, by reaction stoichiometry, the following mass quantities of each compound participate in the reaction:
H₂SO₄: 1 mole× 98 g/mole= 98 gramsNaOH: 2 moles× 40 g/mole= 80 gramsNa₂SO₄: 1 mole× 142 g/mole= 142 gramsH₂O: 2 moles× 18 g/mole= 36 gramsDefinition of molarityMolar concentration or molarity is a measure of the concentration of a solute in a solution and indicates the number of moles of solute that are dissolved in a given volume.
The molarity of a solution is calculated by dividing the moles of solute by the volume of the solution:
[tex]Molarity= \frac{number of moles}{volume}[/tex]
Molarity is expressed in units [tex]\frac{moles}{liter}[/tex].
Moles of H₂SO₄ requiredThe following rule of three can be applied: If by reaction stoichiometry 80 grams of NaOH react with 1 mole of H₂SO₄, 28 grams of NaOH react with how many moles of H₂SO₄?
[tex]moles of H_{2}S O_{4} =\frac{28 grams of NaOHx1 mole ofH_{2}S O_{4} }{80 grams of NaOH}[/tex]
moles of H₂SO₄= 0.35 moles
Volume of H₂SO₄ requiredIn this case, you know:
Molarity= 2 M= 2 [tex]\frac{moles}{liter}[/tex]amount of moles= 0.35 molesReplacing in the definition of molarity:
[tex]2 \frac{moles}{liter}= \frac{0.35 moles}{volume}[/tex]
Solving:
2 [tex]\frac{moles}{liter}[/tex] × volume= 0.35 moles
volume= 0.35 moles ÷ 2 [tex]\frac{moles}{liter}[/tex]
volume= 0.175 liters= 175 mL (being 1 L= 1000 mL)
Finally, 175 mL of 2 M H₂SO₄ will react with 28.0 g of NaOH.
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A sample of compound contains 5.65x10 21 molecules molar mass of the compound is 89.06g/ mol determine the mass of the sample in grams
Answer:
Explanation:
no of molecules=5.65*10^21
NA=6.23*10^23
no of moles=no of molecules/avogadro number
no of moles=5.65*10^21/6.23*10^23
no of moles=9.07*10^-3
now we know that
no of moles=mass/molar mass
mass=no of moles*molar mass
mass=9.07*10^-3*89.06
mass=0.808 g
compare the size of I, I+ and I-
umm explanation pls so i answee
Considering the patterns you have noticed in this activity, which statement best explains why a compound with the molecular formula CH3 doesn't exist in nature?
A. Hydrogen typically needs four bonds to reach a noble gas configuration.
B. Carbon needs more than just three bonds to reach a noble gas configuration. C. The chemical CH3 does not react with other substances because of its high stability.
D. CH3 has three double bonds, which fails to give it a noble gas configuration
Answer:
The answer is B
Explanation:
I had the same question and I chose B and it was correct.
Answer:
B. Carbon needs more than just three bonds to reach a noble gas
Explanation:
PLATO ANSWER
PLATO EXPLANATION-
Each hydrogen atom can make only one bond, but a carbon atom needs four bonds to be stable. Therefore, three hydrogen atoms are not enough for the carbon atom to make four bonds.
The enthalpy change of reaction 1 is -114 kJ mol-1
reaction 1
2NaOH(aq) + H2SO4(aq)
→ Na2SO4(aq) + 2H2O(1)
By using this information, what is the most likely value for the enthalpy change of reaction 2?
reaction 2
Ba(OH)2(aq) + 2HCl(aq) → BaCl2(aq) + 2H2O(1)
Answer:
-114kJ mol-1
Explanation:
Definition of the enthalpy change of neutralization: the energy released with the formation of 1 mole of water when neutralization takes place between an acid and a base.
Since both reactions yield the same number of moles of water, the answer should be -114kJ mol-1.
The statement for the enthalpy change of reaction 2 is "-114 kJ"
What is enthalpy change?The change in enthalpy (ΔH) is a quantity of heat of a system. The enthalpy change is the amount of heat that enters or exits a system during a reaction.
One equivalent of hydrogen ions is neutralised with one equivalent of hydroxide ions in the reaction 1,
NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
The change in enthalpy is given as -114 kJ.
Two equivalents of hydrogen ions are neutralised with two equivalents of hydroxide ions in the reaction 2,
Ba(OH)2 + H2SO4 (aq) → BaSO4 (s) + 2H2O (l)
But, that primary ionic reaction is same for both the reaction in which hydrogen ion combines with hydroxide ion to generate a water molecule. So, the enthalpy change of reaction 1 would be exactly same as for reaction 2.
The neutralization enthalpy comes out to be -114 kJ.
Hence the correct answer is -114 kJ.
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A. The chemical formula for iron (III) sulfate is Fe2(SO4)3. How many atoms of each element are present?
2 iron, 3 sulfur, 12 oxygen
3 iron, 3 sulfur, 12 oxygen
2 iron, 1 sulfur, 4 oxygen
6 iron, 3 sulfur, 12 oxygen
B.How many moles of hydrogen are in 1.8 mole(s) of quinine?
Express your answer using two significant figures.
C. How many moles of carbon are in 5.4 moles of quinine?
Express your answer using two significant figures.
D. How many moles of nitrogen are in 2.0×10−2 mole of quinine?
Express your answer using two significant figures.
Answer:
A. 2 Fe, 3 S and 12 O
B. 43 moles of H
C. 1.0×10² moles of C
Explanation:
A. Formula for iron (III) sulfate is Fe₂(SO₄)₃
This salt has 2 atoms of iron and 3 sulfates, so in total we have:
2 Fe, 3 S and 12 O
Pay attention to the subscripts
B. Formula for quinine is: C₂₀H₂₄N₂O₂
If we continue with the example before we can say that 1 mol of Iron (III) sulfate contains 2 moles of Fe, 3 moles of S and 12 moles of O
Then, 1 mol of quinine contains 24 moles of H
So 1.8 moles of quinine, may contain (1.8 . 24) /1 = 43 moles of H
C. 1 mol of quinine contains 20 moles of C
5.4 moles of quinine may contain (5.4 . 20) /1 = 1.0×10²
(As the answer must be in 2 significant figures and the real answer is 108, I had to use scientific notation)
5. What is the pH of an aqueous solution of the strong acid, Perchloric Acid (HClO4), with a concentration of 0.007 M?
Help me I’ll do anything
Answer:
its not A B or C soo choose D *This is what i think*
Answer:
A) something that causes physical pain
hope this helps
Explanation:
A ballon that contains 0.75 l of gad at 25 c is cooled to - 100 c. Calculate the new volume of the baloon
Answer:
0.44L
Explanation:
Given parameters:
Initial volume = 0.75L
Initial temperature = 25°C = 273 + 25 = 298K
Final temperature = -100°C = 273 + (-100) = 173K
Unknown:
New volume of the balloon = ?
Solution:
According to Charles's law;
"the volume of a fixed mass of a gas varies directly as its absolute temperature if the pressure is constant".
Mathematically;
[tex]\frac{V_{1} }{T_{1} }[/tex] = [tex]\frac{V_{2} }{T_{2} }[/tex]
V and T are temperature values
1 and 2 are the initial and final states
Insert the parameters and solve;
[tex]\frac{0.75}{298}[/tex] = [tex]\frac{V_{2} }{173}[/tex]
298V₂ = 129.75
V₂ = 0.44L
how many elements are present No and NO
1. If a solution of sodium chloride has 22.3 g of
NaCl, and a volume of 2.00 L, what is its molarity?
We are given:
Mass of NaCl in the given solution = 22.3 grams
Volume of the given solution = 2 L
Number of Moles of NaCl:
We know that the number of moles = Given mass / Molar mass
Number of moles = 22.3 / 58.44 = 0.382 moles
Molarity of NaCl in the Given solution:
We know that Molarity of a solution = Moles of Solute / Volume of Solution(in L)
Molarity = 0.382 / 2
Molarity = 0.191 M
Graphite is sometimes used to reduce the friction between
two surfaces that are rubbing together.
Explain how it does this.
Graphite is sometimes used to reduce the friction between two surfaces that are rubbing together. Therefore, this happen because of weak covalent bond.
What is graphite?Graphite is among the most prevalent carbon allotropes. It is also the stable allotrope for carbon, and as such, it is employed in electrochemistry to define the heat of synthesis of carbon compounds. With a hardness of 2.09-2.23 g/cm3, graphite is an excellent conductor of electricity and heat.
Graphite is a large covalent structure in which each carbon atom is covalently linked to three other carbon atoms. Graphite is sometimes used to reduce the friction between two surfaces that are rubbing together. This happen because of weak covalent bond.
Therefore, graphite is sometimes used to reduce the friction between two surfaces that are rubbing together. This happen because of weak covalent bond.
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Which situation describes a chemical change?
A. Clay pressed into a mold takes on the shape of the mold.
B. Baking soda added to vinegar gives off carbon dioxide gas.
C. Chocolate changes from a solid to a liquid when heated.
D. Rubbing pencil lead onto paper changes the color of the paper.
Answer:
C
Explanation:
I just took the test
Answer:
B
Explanation:
Which of the following elements can only form single covalent bonds when forming molecular compounds?
a) Nitrogen
b) Hydrogen
c) Carbon
d) Oxygen
Hydrogen can only form single covalent bonds when forming molecular compounds. Therefore, option B is correct.
What is covalent bond?A covalent bond is a type of chemical bond formed between two or more atoms in which electrons are shared between them. Covalent bonds usually occur between nonmetal atoms and are formed by the sharing of valence electrons.
Hydrogen can only form a single covalent bond because it has only one valence electron and needs one more electron to complete its valence shell, making it stable.
Nitrogen can form triple covalent bonds, carbon can form multiple covalent bonds, and oxygen can form double covalent bonds in molecular compounds.
Thus, option B is correct.
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The internal energy of reaction is -855.1). The reaction has a change of
temperature of 63.20°C that consist of 8.85g of material. Assume the
heat capacity of 2.650J/g °C. What is the work energy of this process..
The work energy of this process : 2337.298 J
Further explanationThe laws of thermodynamics 1 state that: energy can be changed but cannot be destroyed or created
ΔU=Q-W
Q=m.c.Δt
[tex]\tt Q=8.85\times 2.650\times 63.2=1482.198~J[/tex]
the work (W) :
[tex]\tt W=Q-\Delta U\\\\W=1482.198-(-855.1)=2337.298~J[/tex]
What volume of a 0.181 M nitric acid solution is required to neutralize 25.1 mL of a 0.167 M calcium hydroxide solution
Answer:
46.32 mL
Explanation:
We'll begin by writing the balanced equation for the reaction. This is illustrated below:
2HNO₃ + Ca(OH)₂ —> Ca(NO₃)₂ + 2H₂O
From the balanced equation above,
The following data were obtained:
Mole ratio of the acid, HNO₃ (nA) = 2
Mole ratio of the base, Ca(OH)₂ (nB) = 1
Next, we shall write out the data obtained from the question. This includes:
Molarity of the acid, HNO₃ (Ma) = 0.181 M
Volume of the base, Ca(OH)₂ (Vb) = 25.1 mL
Molarity of the base, Ca(OH)₂ (Mb) = 0.167 M
Volume of the acid, HNO₃ (Va) =?
Finally, we shall determine the volume of the acid, HNO₃ as shown below:
MaVa/ MbVb = nA/nB
0.181 × Va / 0.167 × 25.1 = 2/1
0.181 × Va / 4.1917 = 2
Cross multiply
0.181 × Va = 4.1917 × 2
0.181 × Va = 8.3834
Divide both side by 0.181
Va = 8.3834 / 0.181
Va = 46.32 mL
Therefore, the nitric acid, HNO₃ required for the reaction is 46.32 mL
When a metal reacts with hydrogen carbon dioxide gas is produced? True or False
Answer:
false
Explanation:
"When a metal reacts with hydrogen carbon dioxide gas is produced" statement is false.
What is a chemical equation?A chemical reaction is a representation of symbols of the elements to indicate the amount of substance and moles of reactant and product.
Generally, metals do not react with hydrogen. But some metals like sodium, potassium, calcium and magnesium force the hydrogen atom to accept the electrons given by these elements and form salt-like ionic solid compounds called metal hydrides.
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2. Suppose 13.7 g of C2H2 reacts with 18.5 g O2 according to the reaction below. C2H2(g) + O2(g) → CO2(g) + H2O(ℓ) a. What is the mass of CO2 produced? b. What is the limiting reagent?
Answer:
Mass of CO₂ produced = 20.328 g
Oxygen is limiting reagent.
Explanation:
Given data:
Mass of C₂H₂ = 13.7 g
Mass of O₂ = 18.5 g
Mass of CO₂ produced = ?
What is limiting reagent = ?
Solution:
Chemical equation:
2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O
Number of moles of C₂H₂:
Number of moles = mass /molar mass
Number of moles = 13.7 g/ 26.04 g/mol
Number of moles = 0.526 mol
Number of moles of O₂:
Number of moles = mass /molar mass
Number of moles = 18.5 g/ 32 g/mol
Number of moles = 0.578 mol
Now we will compare the moles of CO₂ with C₂H₂ and O₂
C₂H₂ : CO₂
2 : 4
0.526 : 4/2×0.526 = 1.052
O₂ : CO₂
5 : 4
0.578 : 4/5×0.578 = 0.462
The number of moles of CO₂ produced by O₂ are less thus oxygen will be limiting reactant.
Mass of CO₂ produced:
Mass = number of moles × molar mass
Mass = 0.462 mol × 44 g/mol
Mass = 20.328 g
Why is Mg++ smaller than Mg atom?
Answer:
The magnesium ion is much smaller than the magnesium atom because magnesium atom contains more electrons as compared to magnesium ion. Explanation: ... Whereas when an atom tends to lose an electron then it acquires a positive charge and size of the atom tends to increase.
Answer:
Because it looses it two electrons to form a stable octet Ionic form..........
Theodor Schwann was a German scientist who wanted to understand how different types of cells worked and performed functions in different tissues. He was one of the first to theorize that all living things are made up of cells.
Rudolf Virchow was a German doctor who wanted to discover the origin of diseases. He accepted the idea that all living things are made up of cells and extended the idea to theorize that many diseases are the result of bacterial cells infecting the body.
The example described above suggests that
A.
scientific discoveries are never made by doctors.
B.
scientists always have the same goals when making related discoveries.
C.
German scientists were the first to disprove cell theory.
D.
people with different goals can make contributions to scientific knowledge.
D. People with different goals can make contributions to scientific knowledge
Both Schwann and Virchow had different thoughts and ideas. Schwann wanted to understand how cells worked - Virchow wanted to know the origin of diseases. Different goals.
Answer:
D
Explanation:
I got it right on studyisland
find the volume of a gas at standard pressure if its volume at 1.9 atm is 80 ml?
given:
formula:
substitution:
answer:
Answer:
1.5 × 10² mL
Explanation:
Step 1: Given data
Initial pressure of the gas (P₁): 1.9 atmInitial volume of the gas (V₁): 80 mLFinal pressure of the gas (P₂): 1.0 atm (standard pressure)Final volume of the gas (V₂): ?Step 2: Calculate the final volume of the gas
For an ideal gas, we can calculate the final volume of the gas using Boyle's law.
P₁ × V₁ = P₂ × V₂
V₂ = P₁ × V₁/P₂
V₂ = 1.9 atm × 80 mL/1.0 atm
V₂ = 1.5 × 10² mL
Since the pressure decreased, the volume of the gas increased.
sodium hydroxide is extremely soluble in water. a saturated solution contains 678.57 grams of sodium hydroxide 1.00 liter of solution. calculate the molarity of a saturated sodium hydroxide solution.
Answer:
M = 17 M
Explanation:
Given data:
Mass of sodium hydroxide = 678.57 g
Volume of solution = 1.00 L
Molarity of solution = ?
Solution:
Molarity is used to describe the concentration of solution. It tells how many moles are dissolve in per litter of solution.
Formula:
Molarity = number of moles of solute / L of solution
Number of moles of sodium hydroxide:
Number of moles = mass/molar mass
Number of moles = 678.57 g /40 g/mol
Number of moles = 17 mol
Molarity:
M = 17 mol/1.00 L
M = 17 mol/L
M = 17 M
Brad pushed a shopping cart directly toward his car at a constant velocity for 6.0 seconds.
During that time, Brad's daughter jogged past him at 2.4 meters per second, and the cart
moved 6.6 meters. What was the cart's velocity?
Answer:
Watch Naruto that's the answer
Explanation:
What happens to the gravitational potential energy of an object if you bring it higher with respect to the ground? *
Answer:
Increases
Explanation:
The gravitational potential energy of an object increases as you bring it higher with respect to the ground.
Gravitational potential energy depends on the mass, height and gravity between two bodies;
Gravitational potential energy = mgh
m is the mass
g is the height
h is the height
We can clearly see that the higher the elevation, the more the value of the gravitational potential energy.