Iodine-131 has a half-life of 8 days. How long would it take for the number of unstable nuclei in the sample to be reduced from 1,000 to 125?

Answer:

A. Invisible

Explanation:

Answer: Indivisible

Explanation: There was a brilliant philosopher named Democritus, and he proposed the Greek word atomos, which means uncuttable.

Synonyms for uncuttable are as follows:

Joined, inseparable, Indivisible, unbreakable, irreducible, impenetrable, unalterable, indissoluble, unified, permanent, immutable and unchangeable.

Why other answers are wrong:

I simply believe the other user may have had a minor typo which caused such confusion. Who knew one letter could effect an answer that much XD

Answer:

it can be revised at any time.

Explanation:

Answer: Multiple answers to this question. This is what I comprehend.

Explanation:

Upon analysis of the results, a theory can be rejected or modified, but it can never be proven to be correct 100 percent of the time. For example, relativity has been tested many times, so it is generally accepted as true, but there could be an instance, which has not been encountered, where it is not true.

Answer:

d. CH3CH2OH

Explanation:

Molecular solution are solutions when a molecular compound is dissolved in them.

CH3CH2OH represents Ethanol or alcohol carrying "OH" group and is a molecule. CH3CH2OH or Ethanol forms a molecular solution in water.

The equation for Ethanol dissolving in water as follows:

             CH3CH2OH(l) => CH3CH2OH(aq)

CH3CH2OH  srays together as molecules. During dissolving, ethanol molecule fit into spaces between water molecules and completely mix with water.

While HCN, CH3COOH and Ba(OH)2 form ionic solution.

Hence, the correct option is d. CH3CH2OH.

Answer:

Percentage Mass carbon = 14.3%

Explanation:

Baking soda which is sodium hydrogen bicarbonate has the molecular fomula, NaHCO3.

Atomic masses of each of the component atoms is, Na = 23; H = 1; C = 12; O = 16

Step 1: Molar mass of NaHCO3 = 23 + 1 + 12 + 3*16 = 84 g/mol

Step 2: Percentage mass of Carbon = (atomic mass of Carbon / molar mass of NaHCO3) * 100%

= (12 / 84) *100%

Percentage Mass of carbon = 14.3%

Answer:

Need more details to answer correctly.

Do you mean in general why are populations decreasing?

Well for jaguars this is due to poaching and deforestation.

For Sloths this is due to deforestation.

In an ecosystem, the jaguars and sloths  are not growing and thriving due to deforestation and poaching.

Ecosystem is defined as a system which consists of all living organisms and the physical components with which the living beings interact. The abiotic and biotic components are linked to each other through nutrient cycles and flow of energy.

Energy enters the system through the process of photosynthesis .Animals play an important role in transfer of energy as they feed on each other.As a result of this transfer of matter and energy takes place through the system .Living organisms also influence the quantity of biomass present.By decomposition of dead plants and animals by microbes nutrients are released back in to the soil.

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Answer:a

Explanation:

In the position A, the potential energy is maximum and the kinetic energy is  minimum. At the point B, kinetic energy is highest. At the point C, the losing kinetic energy, gaining potential energy and at D, losing potential energy, gaining kinetic energy.

Kinetic energy of moving body is the energy generated by virtue of its position. Potential energy is generated by virtue of its position at a height from the surface. When a body starts moving from rest, its potential energy starts convert to kinetic energy.

As the height increases,  potential energy increases. When an object moves down, its acceleration due to gravity increases and more energy to fall down make its kinetic energy higher.

Thus, the situations can be matched as follows;

A, the potential energy is maximum and the kinetic energy is  minimum. B, kinetic energy is highest.

C, the losing kinetic energy, gaining potential energy and

D, losing potential energy, gaining kinetic energy.

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Answer:

b

Explanation:

electrons lie in the orbits of the atom. they are negatively charged and they are very small in size. they have very less mass than proton. ele tron has 1/1840 mass of proton.

Answer:

Gravel >Sand>Silt>Clay

Explanation:

Sand, Clay, Gravel and Silt

Clay: all particles smaller than 0.002 mm

Silt: all particles within the size range of 0.002-0.05 mm;

Sand: all particles within the size range of  (2.0 mm - 0.05 mm)

Gravel particles are larger than sand, ranging in size from 4.75 mm to 75 mm

Going through the options, the correct option is;

Gravel >Sand>Silt>Clay

Answer:

Central and South American forests.

Explanation: https://brainly.in/question/7540305

Answer:

Solar Energy & Wind Energy

Explanation:

These are renewable energy and can be used used in replacement for fossil fuels.

PLS MARK ME AS BRAINLIEST!!

Answer:

If the reaction is going from left to right it would be synthesis, if going right to left it would be decomposition.

Explanation:

Na2O (s) + 2CO2 (g) + H2O (g) = 2 NaHCO3 (s)

Left Side

Na = 2

O = 6

C = 2

H = 2

Right Side

Na = 2

O = 6

C = 2

H = 2

Ok so is balanced already, though initial equation in question had an error in regards to the left hand side the ) should have been an O.

Hmm

Na2O (s) + 2CO2 (g) + H2O (g) = 2 NaHCO3 (s)

If it was going from right to left would be decomposition

But going from left to right it would be synthesis

Answer:

Explanation:

The temperature changes for the water and the metal is

ΔT (water) = 4.7°C

ΔT (metal) = - 72.9°C

The quantity or amount of heat per unit mass required to raise the temperature of a body by one degree Celsius is known as specific heat. The unit of specific heat are joules or calories per gram per degree Celsius. Specific heat is an intensive property.

Relationship between temperature and heat is expressed as:

Q = mcΔT

where,

Q is heat energy in Joules (J)

m is mass (in grams)

c is specific heat in J/g°C

ΔT is change in temperature

Now calculate the temperature changes for the water

ΔT (water) = T(final) - T(initial)

                 = 27.1 - 22.4

                 = 4.7°C

Now calculate the temperature changes for the metal

ΔT(metal) = T(final) - T(initial)

                = 27.1 - 100

                = -72.9°C

Thus, from the above calculation we can see that the temperature changes for the water and the metal is

ΔT (water) = 4.7°C

ΔT (metal) = - 72.9°C

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Answer:

It will lead to forced migration.

Explanation:

Changes in ecosystems affect living organisms. An ecosystem is a self supporting unit in which there is an exchange of materials and energy between the living and non living parts. The living part of an ecosystem is called its biotic component. This includes the organisms that live within the ecosystem. The nonliving parts of the ecosystem such as topography, rainfall etc are called abiotic components of the ecosystem.

A short-term environmental change usually forces organism to leave an ecosystem in their quest for survival. For instance, when short term environmental changes such as a sudden drop in rainfall causes drought, organisms migrate in order to obtain food and water. This is a forced migration.

Answer:

It will lead to forced migration.

Explanation:

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Answer:

D

Explanation:

when ionic radius gets bigger, the valence electron is repelled further away from the nucleus due to higher number of principal quantum shells. it experiences less electrostatic forces of attraction with the nucleus and requires less energy to remove.

Answer:

Compounds formed from non-metals consist of molecules.

Explanation:

The atoms in a molecule are joined together by covalent bonds. These bonds form when atoms share pairs of electrons.

I hope I helped, please correct me if I'm wrong!

Considering the definition of covalent bond and molecules, compounds formed from only non-metals consist of particles called molecules.

But you have to know that the covalent bond is the chemical bond between atoms where electrons are shared, forming a molecule.

Covalent bonds are established between non-metallic elements, such as hydrogen H, oxygen O and chlorine Cl. These elements have many electrons in their outermost level (valence electrons) and have a tendency to gain electrons to acquire the stability of the electronic structure of noble gas.

The shared electron pair is common to the two atoms and holds them together.

In other words, a covalent bond is a type of chemical bond where two atoms of non-metallic elements join to form a molecule, where the atoms share pairs of electrons from their most superficial layer or valence layer to achieve stability in the molecule and thus complying with the octet rule.

In summary, compounds formed from only non-metals consist of particles called molecules.

Learn more:

Answer:

Oil---> Wood---> Water

Explanation:

Denser things always go on bottom. Since oil is on top is the least dense among those, and then comes wood and then finally water.

Answer:

It's the bottom layer.  

Explanation:

Scientists use the Law of Superposition to determine the relative age of a layer of sedimentary rock:

The oldest rock layer is at the bottom of an undisturbed bed.

Thus, Layer A in the figure below was deposited first.

Answer:

126 grams

Explanation:

What is the mass of two moles of HNO3?

H = 1g/mole = 1+

N = 14g/mole = 3-

O = 16g/mole = 2-

HNO3 = 63g/mole

Answer:

The answer is C3H8 + 5O2 → 3CO2 + 4H2O .

Answer:

[tex]\huge \boxed{\mathrm{C_3 H_8 +5O_2 \Rightarrow 3CO_2 +4 H_2 O}}[/tex]

[tex]\rule[225]{225}{2}[/tex]

Explanation:

[tex]\sf C_3 H_8 +O_2 \Rightarrow CO_2 + H_2 O[/tex]

Balancing Carbon atoms on the right side,

[tex]\sf C_3 H_8 +O_2 \Rightarrow 3CO_2 + H_2 O[/tex]

Balancing Hydrogen atoms on the right side,

[tex]\sf C_3 H_8 +O_2 \Rightarrow 3CO_2 +4 H_2 O[/tex]

Balancing Oxygen atoms on the left side,

[tex]\sf C_3 H_8 +5O_2 \Rightarrow 3CO_2 +4 H_2 O[/tex]

[tex]\rule[225]{225}{2}[/tex]

Answer: 1 mole of any gas has a volume of 22.4 L at STP

Explanation:

According to avogadro's law, 1 mole of every substance occupies 22.4 L at STP and contains avogadro's number [tex]6.023\times 10^{23}[/tex] of particles.

According to ideal gas equation:

[tex]PV=nRT[/tex]

P = pressure of gas = 1 atm (at STP)

V = Volume of gas = ?

n = number of moles = 1

R = gas constant =[tex]0.0821Latm/Kmol[/tex]

T =temperature =[tex]273K[/tex]  (at STP)

[tex]V=\frac{nRT}{P}[/tex]

[tex]V=\frac{1mol\times 0.0820 L atm/K mol\times 273K}{1atm}=22.4L[/tex]

Thus 1 mole of every gas occupies 22.4 L at STP

Answer:

1 mole of any gas has a volume of 22.4 L at STP

Explanation:

ap3xx

Answer:

Explanation:

Skeleton equations are also known as unbalanced equations.

Eg I react Oxygen, Hydrogen and Chlorine and I get Water and Chlorine Gas

H2 + Cl2 = HCl

Left Side

H = 2

Cl = 2

Right Side

H = 1

Cl = 1

As you can see it's not balanced is skeleton equation.

Answer:

1.0456 g and 0.9811g

Explanation:

The measurements that are consistent with the approximate 1 g instruction would be 1.0456 g and 0.9811g.

Analytical balance generally weighs to an accuracy of 4 decimal places. Hence, every other option that is short of being in 4 decimal places is incorrect.

Also, 1.0456 g and 0.9811g when approximated to the nearest whole number give 1 g.

Answer:

41.3 mL OF PENTANE CONTAINS 62.608 *10^-27 CARBON ATOMS.

Explanation:

Volume of Pentane = 41.3 mL

Density = 0.626 g/mL

Since density is defined as mass per unit volume. Calculate the mass:

Density = mass / volume

Mass = density * volume

Mass = 0.626 g/mL * 41.3 mL

Mass = 0.015 g of pentane

Molar mass of pentane C5H12 = ( 12* 5 + 1*12) = 60 + 12 = 72 g/mol

Number of moles = mass / molar mass

Number of moles = 0.015 g / 72 g/mol

Number of moles = 2.08 * 10^-4 moles.

Since 1 mole of pentane contains 5 moles of carbon, we can then calculate how many moles of csrbon 2.08*10^-4 moles will contain

1 mole of pentane = 5 moles of carbon

2.08 *10^-4 moles = x moles

x mole = 5 * 2.08*10^-4

x mole = 10.4 *10^-4 moles of carbon

In other words, 10.4*10^-4 moles of carbon is present in 41.3 mL of pentane

We can then calculate the number of carbon atoms present in the liquid using:

From 1 mole containing 6.02 *10^-23 atoms, 10.4 *10^-4 moles of pentane will contain:

1 mole = 6.02*10^-23 atoms

10.4 *10^-4 moles = (6.02*10^-23 * 10.4 *10^-4) atoms of pentane

= 62.608 *10 ^-27 atoms of pentane.

So therefore, 41.3 mL of pentane will contain 62.608 * 10 ^-27 carbon atoms

The number of C atoms in 41.3 mL of pentane (C₅H₁₂) of density 0.626 g/mL is 2.16x10²³.

To find the number of C atoms in pentane, we need to find the number of moles.

We can calculate the mass from the density:

[tex] d = \frac{m}{V} [/tex]

Where:

d: is the density = 0.626 g/mL

V: is the volume = 41.3 mL

The mass is:

[tex] m = d*V = 0.626 g/mL*41.3 mL = 25.85 g [/tex]

Now, with the molecular weight of the pentane, we can calculate the number of moles:

[tex] \eta = \frac{m}{M} = \frac{25.85 g}{72.15 g/mol} = 0.358 \:moles [/tex]

The number of C atoms can be found with Avogadro's number:

[tex] n_{C} = \frac{6.022\cdot 10^{23} \:atoms}{1\:mol}*0.358 \:moles = 2.16 \cdot 10^{23} \:atoms [/tex]

Therefore, the liquid contains 2.16x10²³ C atoms.

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I hope it helps you!  

Answer:

neon - non metal

Explanation:

Answer:

Answer: Physical Weathering physically breaks the rock, while Chemical Weathering chemically changes the rock causing it to break.

Explanation: Physical Weathering happens naturally causing the rock to break. An example is roots growing into the concrete causing it to crack. Chemical Weathering on the other hand chemically changes the rock by a chemical reaction. An example is acid rain. Gas or other pollution mixing in with water causing acid rain.

hope this helps ;)