An unknown radioactive substance has a half-life of 3.20 hours.If 25.3 g

of the substance is currently present, what mass A0

was present 8.00 hours ago?

Express your answer with the appropriate units.

The Voltage is the pressure from the electrical circuit of the power source that passes the current.

The Voltage is defined as the pressure from the electrical circuit of the power source that will passes the charged electrons that is the current through the conducting loop, it will enable them to do work  because of the illuminating the light. The in simple terms is : voltage = pressure, and it is denoted as the volts and the symbol is the V.

The voltage is described as the force that causes the flow of the charged particles. The Voltage is also called as the electromotive force.

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The style of Vincent Van Gogh's Starry Night (1889) is Post-Impressionism.

Post-Impressionism is an art movement that developed in France in the late 19th century as a reaction against the limitations of Impressionism. It is characterized by a focus on subjective emotions and personal interpretations of the world, as well as an interest in the formal qualities of art, such as color, line, and form.

Van Gogh's work is known for its expressive use of color and texture, and Starry Night is a prime example of his Post-Impressionist style, with its swirling brushstrokes, intense colors, and dreamlike quality.

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The temperature (in °C) given that 0.225 mole of an ideal gas has a volume of 1923 mL and a pressure of 6.00 atm is 351.6 °C

First, we shall list out the various parameters obtained from the question. This is shown below:

The temperature of the ideal gas can be obtain as follow:

PV = nRT

6 × 1.923 = 0.225 × 0.0821 × T

11.538 = 0.0184725 × T

Divide both sides by 0.0184725

T = 11.538 / 0.0184725

T = 624.6 K

Subtract 273 to obtain answer in °C

T = 624.6 - 273 K

T = 351.6 °C

Thus, we can conclude that the temperature of the ideal gas is 351.6 °C

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What would be the same  about the scientist's model probe and the eventual full-scale version of the probe is that; . They would be the same size. Option A

It is likely that the scientist's model probe would be built to replicate the size and proportions of the full-scale version because this would be vital in determining if the full-scale probe could endure the punishing conditions of Jupiter's atmosphere. The dimensions of the model probe and the real probe would therefore likely be the same.

However, it's likely that the model probe's parts weren't exactly the same as those in the actual probe.

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Answer:

constructed as a cylindrical container for the battery cell, and a carbon rod surrounded by a compound with a higher Standard electrode potential (positive polarity), known as the cathode, that collects the current from the manganese dioxide electrode

Explanation:

is this what you are talking about?

Answer:

Found this on Course Hero. Hope this helps?

Explanation:

The half-life of a first-order reaction is given by the following equation:

t(1/2) = ln(2)/k

where t(1/2) is the half-life and k is the rate constant.

From the given information, we know that the partial pressure of FC1O2(g) falls from 0.080 atm to 0.010 atm over 48 minutes. We can use this information to calculate the rate constant as follows:

ln([FC1O2]t/[FC1O2]0) = -kt

where [FC1O2]t is the concentration (in atm) at time t, [FC1O2]0 is the initial concentration (in atm), and k is the rate constant.

Substituting the given values, we get:

ln(0.010/0.080) = -k(48)

Solving for k, we get:

k = 0.1225 min^-1

Now, we can use the equation for the half-life to calculate the answer:

t(1/2) = ln(2)/k

t(1/2) = ln(2)/0.1225

t(1/2) = 5.66 min (rounded to two significant figures)

Therefore, the half-life of the decomposition reaction is 5.66 minutes.

The increased carbon dioxide levels from combustion engines caused a change in the Earth's energy balance. The additional carbon dioxide in the atmosphere allowed less radiation to escape into space, leading to a net increase in energy retained by the Earth.

This increase in energy is known as the enhanced greenhouse effect, which caused the Earth's average temperature to rise. This phenomenon is known as global warming. The rise in temperature has had numerous impacts on the Earth's climate, including more frequent heatwaves, melting ice caps, rising sea levels, and changes in precipitation patterns. The consequences of global warming are extensive and pose a significant threat to human societies and natural ecosystems, making it crucial to reduce greenhouse gas emissions.

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Answer:

when placed in water, a sodium pellet catches on fire as hydrogen gas is liberated and sodium hydroxide forms. chemical change = fire is a sign of chemical reaction.

Explanation:

When placed in water the sodium pellets catch the fire and liberate the hydrogen gas. On mixing with water solid sodium forms a colorless basic solution.

Sodium is a soft metal. It is a very reactive element with a low melting point. Sodium reacts very quickly with water, snow, and ice to produce sodium hydroxide and hydrogen. It is an alkali metal and the sixth most abundant metal on earth. It has a silvery white color.

It has a strong metallic luster. On reacting with oxygen it produces sodium oxide which on reacting with the water produces sodium hydroxide.

It is used to improve the structure of certain alloys and soaps. It is also used in the purification of metals. Sodium is also present in sodium chloride, an important compound found in the environment.

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The number of moles of the water produces by the 1.3 moles of O₂ is 1.00 mol of H₂O. The correct option is C.

The chemical equation is as :

2C₄H₁₀  +  13O₂  ---->  8CO₂ + 10H₂O

The moles of the O₂ = 1.3 moles H₂O

The molar mass of the O₂ = 32 g/mol

2 moles of the C₄H₁₀ produces the 10 moles of the water,

13 moles of O₂ produces the 10 moles of H₂O

The moles of the H₂O = (10/13) × 1.3

The moles of the H₂O = 1 mol

The number of moles of the water is 1 mol of the H₂O and the moles of the oxygen that is O₂ is the 1.3 moles.. Therefore, the correct option is C.

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Answer:

The time it takes for a radio message to travel from a space probe on Mars to Earth when the planets are at a distance of 56 million km can be calculated using the speed of light which is about 299,792,458 meters per second.

To convert the distance from kilometers to meters, we multiply 56 million km by 1000 to get 56 x 10^6 km = 5.6 x 10^10 m.

The time it takes for a radio signal to travel from Mars to Earth is:

time = distance/speed

time = 5.6 x 10^10 m / 299,792,458 m/s

time = 187 seconds

Therefore, a radio message from a space probe on Mars would take about 187 seconds, or just over 3 minutes, to reach Earth when the planets are at a distance of 56 million km.

Double replacement reactions refer to two ionic substances capable to exchange anions and or cations, ie. particles with different charges.

The meaning of Double replacement chemical reactions is based on the fact that these types of reactions are required to change positive or negative charges between chemical materials.

Therefore, with this data, we can see that the meaning of Double replacement chemical reactions is based on the exchange of cations and or anions in the chemical substances that react during such processes.

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Approximately 63.5% of the compound AgNO3 is made of silver.

The atomic mass of silver (Ag) is 107.87 g/mol, and the atomic mass of nitrogen (N) is 14.01 g/mol, and the atomic mass of oxygen (O) is 16.00 g/mol.

The molecular weight of AgNO3 is:

AgNO3 = (Ag atomic mass) + (N atomic mass) + (3 x O atomic mass)

AgNO3 = (107.87 g/mol) + (14.01 g/mol) + (3 x 16.00 g/mol)

AgNO3 = 169.87 g/mol

The percent by mass of silver in AgNO3 can be calculated as:

Percent by mass of silver = (Mass of silver / Total mass of AgNO3) x 100

Since there is only one silver atom in one AgNO3 molecule, the mass of silver in one mole of AgNO3 is equal to the atomic mass of silver, which is 107.87 g/mol.

Therefore, the percent by mass of silver in AgNO3 is:

Percent by mass of silver = (107.87 g/mol / 169.87 g/mol) x 100

Percent by mass of silver = 63.5%

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Blackberries start to grow in the months of late may and early june.

Seasonal fruits are those which grow only in particular time or season of the year. This is the reason why they can be  produced fresh . There is no need of  chemicals for their survival and appearance during their season. Also, it can be hand-picked when it is fully ripened, moreover it contains a rich taste and flavour. Blackberries that are containerized  and hybrid berries can be planted at any time of the year. But, they best  settle in between the late autumn and late spring. During the dormant season i.e  from late autumn to spring  bare-root plants are only available   for immediate planting.

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The exit gas stream average molecular weight is 28.97 g/mol, and there will be 3.0 kg of leftover Phenanthrene in the reactor.

The balanced combustion equation for Phenanthrene is:

C₁₄H₁₀ + 21O₂ → 14CO₂ + 5H₂O

From the equation, we can see that 21 moles of oxygen are needed to combust 1 mole of Phenanthrene. Thus, to burn 10 kg of Phenanthrene, we need:

and

However, the supplied air is 30% less than the requirement, which means only 70% of the required O₂ will be supplied. Therefore, the actual amount of O₂ supplied will be:

Assuming the air is mostly nitrogen, we can calculate the exit gas stream average molecular weight using the following formula:

where 0.79 and 0.21 are the mole fractions of nitrogen and oxygen in air, respectively, and 28.01 and 32 are the molecular weights of nitrogen and oxygen, respectively.

Finally, we can calculate the amount of leftover Phenanthrene in the reactor:

However, this amount is negligible due to the large scale of the reaction. Therefore, we can round it off to:

Leftover Phenanthrene = 3.0 kg

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Answer: c. endothermic reaction.

Explanation: In an endothermic reaction, energy is absorbed or required to break the bonds in the reactants. This means that more energy is required to break the bonds than is released by the formation of new bonds in the products, resulting in a net absorption of energy. In this case, the amount of energy required to break the bonds (1254 kJ) is higher than the energy produced by breaking the bonds (1001 kJ), indicating that the reaction requires an input of energy and is therefore endothermic.

Answer:

c. endothermic reaction

Explanation:

The given information states that the amount of energy required to break the bonds of the covalent compound is 1254 kJ, and the energy produced as a result of breaking the bonds is 1001 kJ.

In an endothermic reaction, the energy required to break the bonds is greater than the energy released or produced. This means that more energy is absorbed from the surroundings than is released during the reaction. In this case, since the energy required to break the bonds (1254 kJ) is greater than the energy produced (1001 kJ), it indicates that the reaction requires an input of energy from the surroundings, making it an endothermic reaction.

Option c, "endothermic reaction," is the correct answer based on the given information.

Answer:

The answer is D

Explanation:

Non metals are:

Hydrogen (H)

Sulphur (S)

Phosphorus (P)

Carbon (C)

Fluorine (F)

Oxygen (O)

Nitrogen (N)

Chlorine (Cl)

Bromine (Br)

Helium (He)

Argon (Ar)

Iodine (I)

Neon (Ne)

Krypton (Kr)

Radon (Rn)

Selenium (Se)

Xenon (Xe)

Answer:

1. Organized information: Mendeleev's periodic law helped organize the then-disparate information about elements into a system that made sense. This made it easier for chemists to understand the nature of the elements and make predictions about their behavior.

We need to fill the acetylene tank to a pressure of 44.29 atm to ensure that we run out of each gas at the same time.

To solve this problem, we need to apply the ideal gas law:

PV = nRT

Applying the ideal gas law for each tank,

PV = NkT

where N is the number of particles, k is Boltzmann's constant, and T is the temperature.

For oxygen:

(155 atm) * (7.00 L)

= N1 * k * T

For acetylene:

(P2) * (2.00 L)

= N2 * k * T

To use up both gases at the same time, we need to use the same number of moles of each gas. So we can set N1 equal to N2:

N1 = N2

Combining the two equations above to solve for P2:

(155 atm) * (7.00 L) = (N1) * k * T

(P2) * (2.00 L) = (N1) * k * T

Dividing the second equation by the first,

P2/P1 = (2.00 L)/(7.00 L)

P2 = (2.00 L)/(7.00 L) * (155 atm)

P2 = 44.29 atm

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The correct statement about cytokinesis is that a cell plate forms in plant cells. Option C is correct.

During cytokinesis, the cytoplasm of the parent cell divides into two daughter cells, each with its own nucleus and organelles. In animal cells, a contractile ring made of actin and myosin filaments forms around the cell's equator and contracts, pinching the cell in two.

In contrast, plant cells build a cell plate, which forms from vesicles produced by the Golgi apparatus, at the cell's equator. These vesicles fuse together and form a new cell wall to separate the two daughter cells. The other three options mentioned in the question are related to mitosis, which is the division of the nucleus, whereas cytokinesis is the division of the cytoplasm. Option C is correct.

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The intermolecular force between [tex]NH_{3}[/tex]  (ammonia) and HF (hydrogen fluoride) molecules is hydrogen bonding.

[tex]NH_{3}[/tex] and HF molecules hydrogen bind. [tex]NH_{3}[/tex] and HF are polar molecules having a significant electronegativity difference between hydrogen and nitrogen and fluorine, respectively. Hydrogen bonding strengthens the dipole-dipole interaction between the molecules.

Hydrogen bonding occurs when a hydrogen atom is covalently bound to a strongly electronegative atom like N, O, or F and attracts an electronegative atom in a neighbouring molecule. NH3's hydrogen atom bonds with HF's fluorine.

No ions are present, although ion-dipole forces exist between ions and polar molecules. NH3 and HF are polar, hence dispersion (London) forces do not apply. NH3 and HF, neutral chemicals, do not connect through ionic bonding. Dipole-dipole forces between NH3 and HF are not the greatest intermolecular force.

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In the given reaction, CO + H [tex]_2[/tex] O ⇌ CO[tex]_2[/tex] + H[tex]_2[/tex], the equilibrium concentration of CO[tex]_2[/tex] and H[tex]_2[/tex] is 0.0113M. The equilibrium concentration of CO and H [tex]_2[/tex] O is  0.0113M.

When the observable qualities, like colour, temperature, pressure, concentration, etc. do not vary, the process is said to be in equilibrium. As "balance" is the definition of the word "equilibrium," it follows which a chemical reaction reflects a balance among the substances and outcomes involved in the reaction. In the given reaction, CO + H [tex]_2[/tex] O ⇌ CO[tex]_2[/tex] + H[tex]_2[/tex], the equilibrium concentration of CO[tex]_2[/tex] and H[tex]_2[/tex] is 0.0113M. The equilibrium concentration of CO and H [tex]_2[/tex] O is 0.0113M.

Therefore, the correct option is option A.

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We would need to 1.39 L of the stock solution and then make up to the 2.54 L mark.

The dilution formula is used to calculate the new concentration of a solution after it has been diluted with a solvent. The formula is:

C1V1 = C2V2

where:

C1 = the initial concentration of the solution

V1 = the initial volume of the solution

C2 = the final concentration of the solution

V2 = the final volume of the solution

By the use of the formula;

C1V1 = C2V2

V1 = C2V2/C1

V1 = 2.54 * 6/11

V1 = 1.39 L

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Answer:

Because their fur doesn't provide much insulation from the cold, opossums typically spend the winter in dens that are dry, sheltered and safe.

Explanation:

Answer:

It finds a den or nest that is open

Explanation:

There are 1.204 × 10²⁴ atoms in 24 grams of carbon.

The number of atoms present in a substance can be calculated by multiplying the number of moles in the substance by Avogadro's number as follows;

no of atoms = no of moles × 6.02 × 10²³

According to this question, there are 24 grams of carbon atom. The number of moles in this carbon is as follows:

no of moles = 24g ÷ 12g/mol = 2mol

no of atoms = 2 × 6.02 × 10²³

no of atoms = 1.204 × 10²⁴ atoms.

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The buffer solution has a pH of 5.36.

To find the pH of this buffer solution, use the Henderson-Hasselbalch equation:

pH = pKa + log([A⁻]/[HA])

where pKa = dissociation constant of acetic acid, [A⁻] = concentration of acetate ions, and [HA] = concentration of acetic acid.

Calculate the concentrations of acetate ions and acetic acid in the solution.

The initial moles of acetic acid are:

moles of acetic acid = volume of acetic acid x concentration of acetic acid

moles of acetic acid = 0.020 L x 0.10 mol/L

moles of acetic acid = 0.002 mol

After mixing with sodium acetate, the total volume of the solution is 50 mL, so the concentration of acetic acid and acetate ions are:

[HA] = moles of acetic acid / total volume of solution

[HA] = 0.002 mol / 0.050 L

[HA] = 0.040 M

[A⁻] = concentration of sodium acetate

[A⁻] = 0.10 M

The dissociation constant of acetic acid is pKa = 4.76.

Now, substitute these values into the Henderson-Hasselbalch equation:

pH = pKa + log([A⁻]/[HA])

pH = 4.76 + log(0.10/0.040)

pH = 4.76 + 0.60

pH = 5.36

Therefore, the pH of the buffer solution is 5.36.

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The variable that determines which "R" value to use in a calculation is pressure (P). The ideal gas law equation, PV = nRT, includes the universal gas constant (R), which has different values depending on the units used for pressure. If pressure is measured in atmospheres (atm), the value of R is 0.08206 L·atm/mol·K. If pressure is measured in pascals (Pa), the value of R is 8.314 J/mol·K. Similarly, if pressure is measured in other units such as torr, bar, or psi, a different value of R should be used. Therefore, the choice of "R" value to use in a calculation depends on the units of pressure being used in the problem.

Answer:C. pressure (P)

Explanation:

The food caloric content of the candy bar is approximately 167 Cal/g.

The first step is to calculate the heat released by the candy bar, which is equal to the heat absorbed by the calorimeter:

q = m × C × ΔT

where q is the heat released by the candy bar, m is the mass of the candy bar, C is the heat capacity of the calorimeter, and ΔT is the temperature change of the calorimeter.

Plugging in the given values, we get:

q = (23.3 g) × (8.72 kcal/°C) × (15.5 °C) = 3,884.6 cal

Next, we need to convert the heat released to nutritional calories per gram:

Cal/g = q/m

Cal/g = 3,884.6 cal / 23.3 g = 166.6 Cal/g ≈ 167 Cal/g (to three significant figures)

As a result, the candy bar's food caloric value is roughly 167 Cal/g.

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