Carbon-14 is a radioactive isotope. It is found in the air in carbon dioxide molecules. The amount of carbon-14 in the air has stayed the same for thousands of years. There is a small amount of radioactive carbon-14 in all living organisms because it enters the food chain.



Once an organism dies, it stops taking in carbon-14. The carbon-14 it contained at the time of death decays over a long period of time, and the radioactivity of the material decreases.



The approximate time since the organism died can be worked out by measuring the amount of carbon-14 left in its remains compared to the amount in living organisms.


In 1991, two hikers discovered a mummified man, preserved for centuries in the ice on an alpine mountain. Small samples from his body were carbon dated by scientists and found to contain 50% carbon-14 remaining. Based on this finding, how old are the remains of the body estimated to be?



A.
About 5,700 years

B.
About 11,400 years

C.
About 22,800 years

D.
Over 30,000 years

Answer:

it will halves

Explanation:

if the volume is doubled then the pressure is halves.

Answer: You can calculate the pH of an acid or base solution given the hydronium ion concentration by using the formula pH = -log [H3O+] or if given the hydroxide ion concentration by the formula [H3O+] = Kw / [OH-], then using the pH = -log [H3O+] formula.

The pH of a solution is calculated using the equation pH = -log[H3O+], which represents the negative logarithm of the hydrogen ion concentration. A pH less than 7 indicates an acidic solution, while a pH greater than 7 denotes a basic solution.

The basic equation used to calculate the pH of a solution is the negative, base-10 logarithm of the hydrogen ion (H+) concentration of the solution. This can be formally written as pH = -log[H3O+]. Using this equation, we can determine the acidity or alkalinity of a solution on a scale from 0 to 14.

A solution with a pH of 7 is considered neutral, with those pH less than 7 being acidic and those pH greater than 7 being basic or alkaline. For example, a solution with a pH 4 is ten times more acidic than a solution with a pH 5 since each pH unit represents a tenfold difference in H+ ion concentration.

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Answer:

-393.5 kJ

Explanation:

E2020

The enthalpy of formation (delta Hf) of carbon dioxide from the reaction of carbon and oxygen is –393.5 kJ/mol

The enthalpy change the of a reaction is the amount of heat given off or absorbed when reactant molecules react to form products molecules.

Carbon reacts with oxygen to produce carbon dioxide (CO2 (g), and enthalpy of formation, delta Hf = –393.5 kJ/mol). This means that 393.5 kJ of heat is given off when 1 mole of carbon dioxide is formed from carbon and oxygen.

Therefore, the enthalpy of formation (delta Hf) of carbon dioxide from the reaction of carbon and oxygen is –393.5 kJ/mol

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Answer:

8L will be the new volume

Explanation:

Let's use the Ideal Gases Law to determine the answer of this question:

Pressure . volume = number of moles . R . T

P . V = n . R . T

We can propose the two situation for the gas:

P₁ . V₁ = n₁ . R . T₁

P₂ . V₂ = n₁ . R . T₂

Notice that R is a constant and n₁ (moles of gas), is not modified with the changes, so we can cancel them.

For the second situation: P₂ = P₁/8 and T₂ = T₁/9

(P₁ . 9L) / T₁ = (P₁/8 . V₂) / T₁/9

(P₁ . 9L) / T₁ . T₁/9 = (P₁/8 . V₂)

P₁ . 1L = P₁/8 . V₂

P₁ . 1L . 8/P₁ = V₂ → 8L

You can also see it, if you put numbers, for example

1 mol of the gas at 1 atm, let's find out the temperature:

1 atm . 9L = 1 mol . 0.082 . T

9/ 0.082 = 110 K

Second situation: 1/8 atm . V = 1 mol . 0.082 . 110/9 K

V = (1 mol . 0.082 . 110/9 K) . 8 atm → 8.02 L ≅ 8L

Answer:

T₂ = 251.6 K

Explanation:

Given data:

Initial temperature = 41°C

Initial volume = 4.87 L

Final volume = 6.08 L

Final temperature = ?

Solution:

Initial temperature = 41°C (41+273.15 = 314.15 K)

The given problem will be solve through the Charles Law.

According to this law, The volume of given amount of a gas is directly proportional to its temperature at constant number of moles and pressure.

Mathematical expression:

V₁/T₁ = V₂/T₂

V₁ = Initial volume

T₁ = Initial temperature

V₂ = Final volume  

T₂ = Final temperature

Now we will put the values in formula.

V₁/T₁ = V₂/T₂

T₂  = V₂T₁ /V₁

T₂ = 4.87 L × 314.15 K / 6.08 L

T₂ = 1529.9 L.K / 6.08 L

T₂ = 251.6 K

Answer:

Na2O

Explanation:

This is because a bond between a metal and a non-metal has occured.

Final answer:

In Na₂O, two sodium atoms transfer one electron each to the oxygen atom, forming a neutral ionic compound with a ratio of two sodium ions to one oxide ion.

Explanation:

Among the options given, the compound in which electrons have been transferred to an oxygen atom is Na₂O. In Na₂O, two sodium (Na) atoms each donate one electron to the oxygen (O) atom. This transfer of electrons is what forms the ionic bond in Na₂O. Each sodium atom becomes positively charged (Na+), and the oxygen atom gains two electrons to become negatively charged (O₂-). This results in the formation of a neutral ionic compound with a ratio of two sodium ions to one oxide ion.

Answer :  The percent abundance of Li isotope-1 and Li isotope-2 is, 6.94 % and 93.1 % respectively.

Explanation :

Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

[tex]\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i[/tex]   .....(1)

Let the fractional abundance of Li isotope-1 be 'x' and the fractional abundance of Li isotope-2 will be '100-x'

For Li isotope-1 :

Mass of Li isotope-1 = 6.01512 amu

Fractional abundance of Li isotope-1 = x

For Li isotope-2 :

Mass of Li isotope-2 = 7.01600 amu

Fractional abundance of Li isotope-2 = 100-x

Average atomic mass of Li = 6.941 amu

Putting values in equation 1, we get:

[tex]6.941=[(6.01512\times x)+(7.01600\times (100-x))][/tex]

By solving the term 'x', we get:

[tex]x=694.048[/tex]

Percent abundance of Li isotope-1 = [tex]\frac{694.048}{100}=6.94\%[/tex]

Percent abundance of Li isotope-2 = 100 - x = 100-6.94 = 93.1 %

The relative abundance of the isotopes are   7.5% and 92.5%.

The relative atomic mass of an atom is the sum of the products of the relative atomic masses of its isotopes and their respective percentage abundance. We have been told in the question that the relative atomic  mass of Li is 6.941 amu. Let the percentage abundance be x and 1-x

6.941 =  6.01512x +  7.01600(1 - x)

6.941 =  6.01512x +  7.01600 - 7.01600x

6.941 -  7.01600 = -1.00088x

-0.075 = -1.00088x

x = -0.075/-1.00088

x = 0.075

Hence, the other isotope is 1 -  0.075 = 0.925

Therefore, the relative abundance of the isotopes is 7.5% and 92.5%

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Option A. The sample contains Uranium-235.

Most of the uranium used in current nuclear weapons is approximately 93.5 percent enriched uranium-235. Nuclear weapons typically contain 93 percent or more plutonium-239, less than 7 percent plutonium-240, and very small quantities of other plutonium isotopes.

Uranium is the fuel most widely used by nuclear plants for nuclear fission. Uranium is considered a nonrenewable energy source, even though it is a common metal found in rocks worldwide. Nuclear power plants use a certain kind of uranium, referred to as U-235, for fuel because its atoms are easily split apart.

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Answer: a) 49.8 gram

b) 47.0 %

Explanation:

First we have to calculate the moles of glucose

[tex]\text{Moles of glucose}=\frac{\text{Mass of glucose}}{\text{Molar mass of glucose}}=\frac{97.5g}{180.15g/mole}=0.54moles[/tex]

The balanced chemical reaction will be,

[tex]C_6H_{12}O_6\rightarrow 2CH_3CH_2OH+2CO_2[/tex]

From the balanced reaction, we conclude that

As,1 mole of glucose produce = 2 moles of ethanol

So, 0.54 moles of glucose will produce =  [tex]\frac{2}{1}\times 0.54=1.08[/tex] mole of ethanol

Now we have to calculate the mass of ethanol produced

[tex]\text{Mass of ethanol}=\text{Moles of ethanol}\times \text{Molar mass of ethanol}[/tex]

[tex]\text{Mass of ethanol}=(1.08mole)\times (46.08g/mole)=49.8g[/tex]

Now we have to calculate the percent yield of ethanol

[tex]\%\text{ yield of ethanol}=\frac{\text{Actual yield}}{\text{Theoretical yield }}\times 100=\frac{23.4g}{49.8g}\times 100=47.0\%[/tex]

Therefore, the percent yield is 47.0 %

Final answer:

The theoretical yield of ethanol from the fermentation of 97.5 g of glucose is 49.3 g. The percent yield is 47.4% if the actual yield of ethanol is 23.4 g.

Explanation:

To determine the theoretical yield of ethanol, we need to calculate the molar ratio between glucose and ethanol. According to the balanced equation, for every mole of glucose, two moles of ethanol are produced. Therefore, we can set up a proportion and solve for the theoretical yield:

(97.5 g glucose / 180.15 g/mol) x (2 mol ethanol / 1 mol glucose) x (46.08 g/mol) = 49.3 g ethanol

For the percent yield, we can divide the actual yield (23.4 g) by the theoretical yield (49.3 g) and multiply by 100:

(23.4 g / 49.3 g) x 100 = 47.4%

Answer:C) More energy was absorbed in the breaking of chemical bonds than released in the formation of chemical bonds.

Explanation:

Answer:

Budding- A new organism growing from the body of the parent

Fragmentation- The parent breaks into parts that may regenerate into offspring

Binary Fission- The parent cell divides to produce a genetically identical cell

Answer: A new organism growing from the body of the parent

Fragmentation- The parent breaks into parts that may regenerate into offspring

Binary Fission- The parent cell divides to produce a genetically identical cell

Answer:

we cant see them since they are delayed by light years

Explanation:

Answer: The reason why galaxies appear so different between our local universe and the distant one is because we are observing galaxies at different stages of their evolution as we look out in space. Telescopes are time machines, albeit ones that run only in reverse, and so the farther out we look with them, the progressively younger universe we see. Furthermore, we do not observe the universe from any special vantage point. So if we make the reasonable assumption that the physical laws we measure in the local cosmos are universal, we can conclude that the galaxies we observe in the early universe are analogous to the predecessors of the local galaxies. Thus, the differences we see between the different populations of galaxies provide direct insights into the nature of galaxy evolutio

Answer:

the first one

Explanation:

as it contains in the product N so its the forst

Answer:

The pressure of CH3OH and HCl will decrease.

The final partial pressure of HCl is 0.350038 atm

Explanation:

Step 1: Data given

Kp = 4.7 x 10^3 at 400K

Pressure of CH3OH = 0.250 atm

Pressure of HCl = 0.600 atm

Volume = 10.00 L

Step 2: The balanced equation

CH3OH(g) + HCl(g) <=> CH3Cl(g) + H2O(g)

Step 3: The initial pressure

p(CH3OH) = 0.250atm

p(HCl) = 0.600 atm

p(CH3Cl)= 0 atm

p(H2O) = 0 atm

Step 3: Calculate the pressure at the equilibrium

p(CH3OH) = 0.250 - X atm

p(HCl) = 0.600 - X atm

p(CH3Cl)= X atm

p(H2O) = X atm

Step 4: Calculate Kp

Kp = (pHO * pCH3Cl) / (pCH3* pHCl)

4.7 * 10³ =  X² /(0.250-X)(0.600-X)

X = 0.249962

p(CH3OH) = 0.250 - 0.249962 = 0.000038 atm

p(HCl) = 0.600 - 0.249962 = 0.350038 atm

p(CH3Cl)= 0.249962 atm

p(H2O) = 0.249962 atm

Kp = (0.249962 * 0.249962) / (0.000038 * 0.350038)

Kp = 4.7 *10³

The pressure of CH3OH and HCl will decrease.

The final partial pressure of HCl is 0.350038 atm

Final answer:

One liter of 1 M NaOH can completely neutralize one liter of 0.50 M H2SO4 because 1 mole of NaOH is needed to neutralize 0.5 mole of H2SO4, according to the stoichiometric relationship in the balanced chemical equation. So the correct option is d.

Explanation:

To determine which molarity of H2SO4 will be completely neutralized by one liter of 1 M NaOH, we need to look at the stoichiometry of the reaction. Sulfuric acid is a diprotic acid, meaning it can donate two protons (H+). The balanced chemical equation for its reaction with sodium hydroxide (NaOH), which is a monoprotic base, is:

       H2SO4(aq) + 2NaOH(aq) → Na2SO4(aq) + 2H2O(l)

From this equation, we can see that it takes two moles of NaOH to neutralize one mole of H2SO4. Therefore, one liter of 1 M NaOH contains one mole of NaOH, and it can completely neutralize 0.5 mol of H2SO4. If we have one liter of H2SO4, the molarity that would supply 0.5 mol would be 0.50 M, because 0.50 mol/L × 1 L = 0.5 mol. The correct answer is option d - 0.50 M H2SO4.

Answer:

The volume is occupies by 21,0g of methane is 32, 3 L.

Explanation:

We use the formula PV=nRT. We convert the unit temperature Celsiud into Kelvin: 0°C=273 K---> 27°C= 27+273= 300K. We calculate the weight of 1 mol of CH4:

Weight 1 mol CH4= Weight C+ (Weight H)x4= 12 g+ 1g x4= 16 g

16 g---1 mol CH4

21g---x= (21g x 1 mol CH4)/16g= 1, 31 mol CH4

PV=nRT    ----> V= (nRT)/P

V= (1, 31 mol x 0,082 l atm/K mol x 300 K)/ 1 atm

V= 32, 3875 L

The volume occupied by 21.0 g of methane (CH4) at 27 degree celsius and 1 atm is 32.3L

PV = nRT

Where;

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Answer:

pOH is 2.2

Explanation:

The pH scale goes from 0 to 14. As such, the pH and the pOH add up to 14. Subtract your pH from 14 to get your answer.

14 - 11.8 = 2.2

Answer:

32.4 K

Explanation:

From the given parameters;

Initial pressure P1= 50.0 mmHg

Initial temperature T1= 540K

Final Temperature T2 = ?????

Final pressure P2=3 mmHg

Now using this relationship;

P1/T1 = P2/T2

We have; P1T2= P2T1

Hence;

T2= P2T1/P1

T2= 3 ×540/50.0

T2= 32.4 K

Answer:

b

Explanation:

Answer:

D) 0.001 M AlCl3

Explanation:

The solution with the lowest freezing point would be 0.001 M AlCl3 because it produces the most particles when fully ionized in water, therefore lowering the freezing point the most.

Theoretically, the aqueous solution that will have the lowest freezing point is D) 0.001 M AlCl3. This is based on the principle of colligative properties, which states that the freezing point of a solution is lowered when solutes are added. The extent of this lowering depends on the number of solute particles present. In this case, AlCl3, when fully ionized in water, produces 4 particles (1 Al3+ and 3 Cl-), contributing to the greatest decrease in freezing point.

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Answer:

Na2S

Explanation:Just took the test

The chemical formula for the compound formed between sodium and sulfide is Na2S. Sodium has a positive charge and sulfide has a negative charge, which balance when combined in the proportions indicated by the formula.

The chemical formula for the ionic compound formed between the sodium cation, Na+, and the sulfide anion, S²-, is Na2S. This is derived from the fact that sodium (Na) has a positive charge and sulfide (S) has a negative charge.

To balance these charges and form a neutral compound, you need two sodium ions for every sulfide ion. Hence the '2' in Na2S.

This indicates there are two sodium ions in the compound.

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Answer:

Explanation:

hydrogen bond is a bond that is formed as a result of intermolecular forces that exist between hydrogen

and other atoms of electronegative elements such as oxygen and carbon. Since covalent bond is more stronger than hydrogen bond, with this it helps to hold DNA , proteins, molecules together, it brings about the stability of the double helix structure of DNA.

Therefore,it is useful for the base pairs of DNA to be held together by hydrogen bonds and not covalent bonds because Hydrogen bonds are crucial in DNA synthesis. and also it very easy for hydrogen bonds to be broken than covalent bonds. As a result of this, DNA can be easily unwind.

Hydrogen bonds hold DNA bases together because B. hydrogen bonds are easier to break allowing for DNA copying .

Covalent bonds would be too strong, hindering these processes.

Thus, the correct answer is B. hydrogen bonds are easier to break allowing for DNA copying.

Correct question is: Why are hydrogen bonds holding DNA bases together instead of covalent bonds?
A. hydrogen bonds are stronger than covalent bonds
B. hydrogen bonds are easier to break allowing for DNA copying
C. enzymes cannot break covalent bonds
D. covalent bonds cannot attach purines and pyrimidines

Answer:

The rate of the reaction is proportional to the square of the concentration of the reactant.

Explanation:

Let us assume a hypothetical reaction in which the rate determining step is the elementary reaction;

2A------> A2

The rate of reaction will be given by:

Rate= k[A]^2

Hence for a second order reaction having only one reactant, the rate of reaction is proportional to the square of the concentration of the reactant. The proportionality constant k, is known as the rate constant of the reaction.

Answer:

A

Explanation:

I did the test

The coastal erosion landform change due to destructive processes is most easily controlled by human intervention. Therefore, option A is correct.

The term coastal erosion is defined as the process by which local sea level increase, strong wave action, and coastal flooding wear down or carry away rocks, soils, and sands along the coast.

Coastal erosion is caused by hydraulic action, abrasion, impact and corrosion by wind and water, and other forces, natural or unnatural. The softer areas filled with sediment eroded from hard areas, and rock formations are eroded away.

Human activity can rise rates of coastal recession by interrupting the operation of the sediment cell. The construction of major dams of rivers can detain river sediment behind the dam wall.

Thus, option A is correct.

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Answer:

The new rms speed is 1.414 times the original rms speed

Explanation:

The rms speed (root-mean-square speed) of the molecules in a gas can be found by using the formula:

[tex]v=\sqrt{\frac{3RT}{M}}[/tex]

where

R is the gas constant

T is the absoolute temperature (in Kelvin) of the gas

M is the molar mass of the gas (the amount of mass per unit mole)

We can rewrite the equation as

[tex]v\propto \sqrt{T}[/tex] (1)

which means that the rms speed is proportional to the square root of the temperature.

In this problem, we are told that the absolute temperature of the gas is doubled, so the new temperature is

[tex]T'=2T[/tex]

Therefore, according to eq(1), we find that the new rms speed will be:

[tex]v\propto \sqrt{T'} = \sqrt{2T}=\sqrt{2} \sqrt{T}=\sqrt{2}v=1.414v[/tex]

So,

The new rms speed is 1.414 times the original rms speed

If the absolute temperature of a gas is doubled ; ( D ) The new rms speed is 1.414 times the original rms speed

The r.m.s speed of molecules in a gas can be calculated using the formula below ;

[tex]v = \sqrt{\frac{3RT}{M} }[/tex]

T = absolute temperature

R = gas constant

M = molar mass

Also ; The rms speed of gas molecules is directly proportional to [tex]\sqrt{T}[/tex]

i.e.    v ∝ √T  ----- ( 1 )

Given that the absolute temperature ( T ) is doubled the new value of T = 2T

Back to equation ( 1 )

v = √2T  = √2 * √T

  = 1.414

Hence we can conclude that If the absolute temperature of a gas is doubled The new rms speed is 1.414 times the original rms speed.

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Answer:

the third one

Explanation:

they change overtime

Answer:

The answer to your question is   P2 = 0.78 atm

Explanation:

Data

Temperature 1 = T1 = 263°K                 Temperature 2 = T2 = 298°K

Volume 1 = V1 = 24 L                             Volume 2 = V2 = 35 L

Pressure 1 = P1 = 1                                  Pressure 2 = P2 = ?

Process

1.- To solve this problem use the Combined gas law

                          P1V1/T1 = P2V2/T2

-Solve for P2

                           P2 = P1V1T2 / T1V2

-Substitution

                          P2 = (1)(24)(298) / (263)(35)

-Simplification

                          P2 = 7152 / 9205

-Result

                          P2 = 0.777

   or                    P2 = 0.78 atm

The final pressure of the gas is 0.686 atm.

To determine the final pressure of the gas, we can use Boyle's Law, which states that for a fixed amount of gas at a constant temperature, the product of the initial pressure and initial volume is equal to the product of the final pressure and final volume. In this case, we can write:

P1V1 = P2V2

Substituting the given values:

(1.00 atm)(24.0 L) = P2(35.0 L)

Solving for P2:

P2 = (1.00 atm)(24.0 L) / (35.0 L) = 0.68571 atm (rounded to 3 sig figs)

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Final answer:

Untreated sewage dumped into a river causes significant harm to aquatic life, leading to sickness and fatalities among animals, degradation of water quality, and the creation of dead zones. These pollutants also pose a risk to human health as they can travel up the food chain.

Explanation:

The effect of untreated sewage being dumped into a river on the animals living therein is typically devastating. The correct answer to the question, 'What effect has the raw sewage had on the animals that live in the river?' is C) Many animals have become sick or have been found dead.

Water pollution from untreated sewage includes harmful bacteria and chemicals that can cause disease and death in river ecosystems. Pollutants like nitrogen and phosphorus can lead to eutrophication, which depletes the oxygen in the water, creating dead zones where fish and other aquatic life cannot survive. Additionally, contaminated water can carry diseases and toxins up the food chain, posing health risks to animals and humans alike.

Industrial waste and agricultural runoff also contribute to the degradation of water quality, affecting not only the immediate area but also environments downstream. This contamination has a cascading effect on ecosystems, harming countless plants, animals, and humans who depend on these water sources.

Final answer:

The correct answer when a beam of light hits an object is that the light can be reflected, absorbed, or transmitted, depending on the material's properties. It is not exclusive to one single outcome.

Explanation:

When a beam of light hits an object, several outcomes are possible depending on the properties of the material: it can be reflected, absorbed, or transmitted. Reflection occurs when light waves bounce off an object, like seeing your reflection in a glass window. Absorbance happens when a material takes in the energy of a light wave, which may later be re-emitted in some cases, such as with phosphorescence. Lastly, transmission is when light passes through a material, like sunlight through a clear glass. So, when a beam of light hits an object, the correct answer is that all the light is not necessarily absorbed, reflected, or transmitted exclusively; it can be a combination of these interactions.

Answer:

Ca, also known as Calcium

Explanation:

Get a periodic table. In the top left hand corner are of each element's box is a number. This is how many protons are present. Protons are equal to electrons, therefore calcium has 20 electrons. It is in group 2A period 4 if that helps.