What is TRUE about expert witnesses?

A.
They offer personal and professional knowledge.

B.
They are not allowed to practice their testimony.

C.
They are required to link all evidence to the crime.

D.
They have all written a book about their area of expertise.

Option B is correct

Given the chemical reaction below;

The equilibrium constant for the reaction is given as;

Given the following parameters

Substitute

Therefore the equilibrium constant for the reaction is 1.7 * 10^-3

The rate constant ( k )= 9.2 x 10⁻³ s⁻¹The half life  (t1/2 )= 75.3 s

It is given that the reaction is 46% complete in 45 s

The relation between rate constant and the half life can be shown as:

For first order reaction:

ln[A]=−kt+ln[A]o

46% complete, 54% remains

A = 0.54

Ao = 1

Put the value of given data in the formula:

ln A = -kt + ln Ao

ln 0.54 = -k.45 + ln 1

-0.616=-k.45

k = 13.6 x 10⁻³ s⁻¹

The half life can be determined by using the formula:

t1/2 = (ln 2) / k

t1/2 = 0.693 / 13.6 x 10⁻³

t1/2 = 0.0509 ×10⁻³ s.

t1/2 = 5.09 ×[tex]10^{5}[/tex] s.

Therefore, the rate constant for the first order reaction will be 13.6 x 10⁻³ s⁻¹ and half life will be 5.09 ×[tex]10^{5}[/tex] s.

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Introduction

Water is a molecule that composed of chemical elements oxygen and hydrogen. Waterrogen. Water behaves differently than other substances, this is because water can be changed from being a solid to liquid or a gas (vapour). This is known as changing state of matter. Water is a liquid at room temperature, however, it becomes a solid when the temperature is cooled down. The same water can turn into vapour or gas if it is heated up to a certain temperature. Therefore the state of water depends on the temperature.

Solid water

At a temperature below or equal to zero degrees Celsius, the water molecule turns to be a solid (ice), this is called freezing. At this state the water molecules are packed close together, this prevents water from changing its shape, thus, the atoms in solid water are not active, even when ice is removed from its container, it retains its shape. Water in its solid state has a very regular pattern whereby the water molecules are apart from one another and are connected by hydrogen bonds which forms a crystalline lattice. These crystals have a number of open regions and pockets which makes ice less dense than liquid water. This is the main reason ice floats on water. In the solid state, there is not enough thermal energy to overcome the intermolecular forces (hydrogen bonding), thus particles vibrate around fixed axes.

Liquid water

When the ice is warmed from its freezing point, the water molecule changes from solid to liquid water, when the temperature is higher than zero but lower than 100 degrees Celsius. This process is called melting. The attractive forces between the water molecules weaken and individual molecules begin to move around each other, but they are still attracted to each other. Since liquid water molecules can move around, this state can take the shape of its container. The spacing of liquid water molecules per unit volume are actually smaller than it is for solid water, which means liquid water is more denser than solid water. Liquid water have no definite shape, however, has a definite volume.

Gas water

The third state of water is its gaseous state. In this state water molecules move freely and rapidly because they are not bound together. The change form liquid to vapour or gas is called vaporization, this process occurs at a temperature of 100 degrees Celsius. Gas water molecules have no definite shape, nor definite volume. Particles or atoms move randomly and are less attracted to each other. Gas water molecules are highly compressible.

Conclusion

Water exists in three forms or states. These include solid, liquid and gaseous states. Water is a liquid at room temperature, whereas it is a solid at temperatures below or equal to zero. When the water is heated up to 100 degrees Celsius, it turns to a gaseous state.

In the given illustration, it is observed that at first molecules are dispersed without any type of configuration or order and they adapt to the container shape. It means that they represent a liquid.

At the second stage, molecules are ordered and they have a defined shape, which is characteristic of solids.

It means that the change converted a liquid into a solid.

This is known as freezing. A liquid is frozen to became a solid, one example is water and ice.

It means that the correct answer is Freezing.

During freezing you release energy, this is because the liquid has to lose heat to become a solid. The answer to the second part is releases.

Action and response are two forces that have the same magnitude but opposing directions.

Explanation.

The force used by a dog as it moves across the ground is known as the action force. The force that the earth exerts on the dog is the reaction force, on the other hand. Newton's third law of motion serves as its foundation.

When we walk on the ground, we push the earth backward with our feet, but the ground pushes our feet forward with an equal force, which propels us forward. Because of this, the action is the force that pushes the ground backward, and the reaction is the force by the ground on our feet.

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827.76 m/60.65 s = 13.65 m/s

685.5 mol/0.50 L = 1371 mol/L

20.9476 cm x 26 cm = 545 cm^2

When adding/subtracting

Use the least number of significant figures past the decimal point when adding or subtracting numbers.

When multiplying/dividing

Use the least number of significant figures present in any number in the problem when multiplying or dividing numbers.

To solve this question we will use the integrated rate late law for first order reaction:

By substituting the values we have to determine the unknown we get:

Answer: Rate constant k is 6.392x10^-4 per min.

Solutions :

We are given

• mass of potassium = 2.75 g

• Recall that 1 mole of potassium = 39.0983 grams

So , 2.75 g will represent

By following Daltons laws of partial pressure .

" the pressure that eachgaswould have exerted ,Add up to the total pressure" .

• Therefore :

• Total Pressure = P.Pressure (oxygen) + P.Pressure of (He)

15 atm = 6atm + Pressure of He

P.Pressure ofHe = 15atm-6atm

= 9 atm

This means that the partial pressure of He = 9atm +

An Arrhenius base is a compound which ionizes to yield hydroxide ions (OH−) in aqueous solution.

We can see that the solution has a boiling point of 80.93°C.

The atmospheric pressure does equal the pressure of a liquid as we heat the system. The temperature at which this occurs is called the boiling point. Now we know that the boiling point of the pure benzene is 80.1 °C.

Given that;

ΔT = K m i

ΔT = boiling point elevation

K = boiling point constant

m = molality of the solution

i = Van Hoff factor (molecular solute)

ΔT = 2.53°C /m * 0.33 m * 1

ΔT =  0.83°C

The boiling point of the solution is now gotten from ; 0.83°C + 80.1 °C

= 80.93°C

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Answer:

Explanation:

Here, we want to get the definition of a weak base

A weak base is a base that does not dissociate completely in solution.

What this means is that when the base is placed in a solution, its dissociation into the corresponding metallic and hydroxide ions is incomplete

Surfactants are characterized to lower the surface tension between two liquids or between a liquid and a gas and so on.

You can see an example for detergents: the detergents are surfactants that lower the surface tension and that's because you can see that the dirt disperses easily and other substances, so the answer is false.

Answer:

The car will most likely move the fastest on the wood. Carpet will create drag due to the friction between the car's wheels and the carpet. Bricks are not smooth so drag will occur, however it will be minimal. Wood is usually smooth and there is almost no drag or friction...the car will glide easily over the surface.

Explanation:

Hope this helps!!

Answer:

the answer is A since the foot is printed

Answer:

It represents a trace evidence,since it leads to a suspect

The mass of 0.0750 moles of calcium is 3.01g.

To calculate the mass of calcium we need to use the molar mass that we can find in the Periodic Table of Elements.

The molar mass of calcium is 40.1 g/mol.

Now, with a mathematical Rule of Three we can calculate the mass of calcium of 0.0750 moles:

So, the mass of 0.0750 moles of calcium is 3.01g.

If 30.0 mL of 0.150 M CaCl2 is added to 22.0 mL of 0.100 M AgNO3 then  0.0022 moles AgNO3 will be precipitated.

The balanced chemical equation can be written as:

[tex]2AgNO_{3}[/tex] + [tex]CaCl_{2}[/tex] → 2AgCl + [tex]Ca(NO_{3} )_{2}[/tex]

Molecular Weight of CaCl2 = 110.98 g/mol

[tex]Ca(NO_{3} )_{2}[/tex] =170.01

AgCl = 143.45 g/mol

Volume of calcium chloride ([tex]CaCl_{2}[/tex] ) =30.0mL

1 ml = [tex]10^{-3}[/tex] L

So, 30 ml =0.03L

[tex]AgNO_{3}[/tex] = 22 mL= 0.022 L

1 ml = [tex]10^{-3}[/tex] L

So, 22 ml =0.022 L

By solving for the limiting reactant one needs to get the moles [tex]CaCl_{2}[/tex]and mols [tex]AgNO_{3}[/tex].

calcium chloride ( [tex]CaCl_{2}[/tex] )  = 0.150M(mol/L) × 0.03L = 0.0045 moles

Silver nitrate ([tex]AgNO_{3}[/tex] ) = 0.100M ×0.022L = 0.0022 moles

Since the stoichiometric ratio of Silver nitrate ( [tex]AgNO_{3}[/tex] ) to calcium chloride ( [tex]CaCl_{2}[/tex]) is 2:1

0.0022 mols [tex]AgNO_{3}[/tex] × (1 mol  [tex]CaCl_{2}[/tex] / [tex]AgNO_{3}[/tex] 2 mols ) = 0.00085 mols  [tex]CaCl_{2}[/tex] .

Therefore, 0.0022 moles [tex]AgNO_{3}[/tex] will be obtained.

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First, we have to remember what a mass percentage means (in this particular case):

It is the amount of each element in a compound, and it is calculated as follows:

The addition of the different mass percentages is equal to 100%.

In this case, we have the percentage of one of the elements of the compound, we can make the respective subtraction:

Then, the answer is that the iodine mass percentage is 86.4%

A)Nuclear fusion releases protons and neutrons, so the total number of protons and neutrons in a star changes throughout its life is the true statement.

A suggested method of producing energy would use heat from nuclear fusion processes to produce electricity. A heavier atomic nucleus is created by the fusion of two lighter ones, which also produces energy. Fusion reactors are devices created to use this energy.

Nuclear fusion is less risky than nuclear fission because the fuel rods produced by nuclear fission include dangerous radioactive waste that may be used in weapons and must be maintained carefully for thousands of years.

Powering the Sun and other stars are nuclear fusion processes. Two light nuclei combine to produce one heavy nucleus during a fusion process. The resultant single nucleus's total mass is less than the mass, which causes the process to release energy.

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The wavelength of the light in this case is 92 nm

In accordance with the Bohr model of the atom, We know that electrons could be promoted from the from a lower to a higher energy level. As such, the movement of the electron would lead to the emission of light of a characteristic wavelength.

Hence;

1/λ = 1.097 * 10^7 (1/[tex]n_{2} ^{2}[/tex] - 1/[tex]n_{1} ^{2}[/tex])

Hence;

n1 = 1

n2 = 12

We then have;

1/λ = 1.097 * 10^7 (1/1^2 - 1/12^2)

1/λ = 1.097 * 10^7 (1 - 0.0069)

λ = 9.2 * 10^-8 m or 92 nm

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Answer:

Explanation:

Here, we want to get the molar volume of the gas

At STP, 1 mole of a gas occupies a volume 0f 22.4 dm^3

The conditions at STP are 273K

The Lewis Structure for NH₄⁺ (Ammonium ion) is described as having four sigma bonds around a Nitrogen Atom. It is also to be noted tha there is a +1 charge on the Nitrogen atom.

The nitrogen atom is surrounded by four sigma bonds. As a result, the form of NH4+ is tetrahedral. The total number of sigma bonds and lone pairs surrounding the nitrogen atom is four. As a result, the geometry should be tetrahedral.

Lewis structures also referred as Lewis dot formulas, Lewis dot frameworks, electron dot structures, or Lewis electron dot structures, are schematics that depict the bonding between atoms in a molecule as well as any lone pairs of electrons that may occur.

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1) Converting grams to moles or moles to grams

In order to do this kind of conversion, we need the molar mass (in grams) of the compound to use it as a conversion factor as follows:

-

The total energy to break the hexane bonds will be equal to the sum of each of the energy to break each bond.

So the first thing we're going to do is determine how many and what type of bonds hexane has. Hexane is an alkane, meaning the C-C bonds are all single bonds. We also have C-H bonds. According to the structure of hexane, we will count each of the bonds in the following figure:

The number of C-H bonds is written in blue, we see that there are 14 C-H bonds, which coincides, being an alkane, with the number of hydrogen atoms.

The number of C-C bonds is written in orange. The number of C-C bonds is equal to 5.

Now, we multiply the energy to break each bond by the number of bonds and add the energy of the C-H and C-C bonds.

So, for 1 mol of hexane the energy. required to break all the bonds will be 7514kJ

Answer: The closest value to the answer is 7520. D) 7520 kJ

Option B.   All cobalt atoms are identical and are consistent with dalton's atomic theory as it was originally stated.

The primary part of dalton's atomic theory states that everyone relies on is manufactured from atoms, which can be indivisible. the second part of the theory says all atoms of a given element are the same in mass and house. The 0.33 part says compounds are combos of two or more exceptional kinds of atoms.

Dalton's atomic theory, atoms of one element are all the equal or same. for this reason, the assertion that every cobalt atoms are identical is consistent with Dalton's concept of the shape of atoms.

Dalton's atomic concept additionally proposed that each atom of an element is identical in nature and exceptional elements vary in length, mass, and chemical properties. So, the accurate answer is choice 1 which says that the first and 2d statements are correct.

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The concentration of C₂H₅OH in the resulting solution is 1.332 M.

given that :

mass of C₂H₅OH = 30.7 g

molar mass =46.07 g/mol

volume =  500 ml = 0.5 L

number of moles can be calculated by the following formula :

number of moles = mass / molar mass

no. of moles = 30.7 g / 46.07 g/mol

no. of moles = 0.666 mol

now, the concentration of C₂H₅OH :

Molarity = no. of mole / volumes in l

Molarity = 0.666 / 0.5

Molarity = 1.332 M

Thus, If 30.7 g of C₂H₅OH (MM = 46.07 g/mol) are added to a 500.0 mL volumetric flask, and water is added to fill the flask, The concentration of C₂H₅OH in the resulting solution is 1.332 M.

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b) firstly we nee dto understant that 1 ton = 2831.68 litres

therefore if 16 967.04 Litres needs transporting we simply divide the 16 967.04 by 2831.68 and the answer is 5.99 which is rounded of to 6. therefore 6 trucks will be needed

c) we need to first find out how many gallons of fuels will be needed to complete a 285 mile distance. so we divide 285 by 7.8 to get 36.54 gallons and we know the price of i gallon to be $3.95 therefoe the cost will be

3.95 x 36.54 = 144.33

the cost is $144.33 per day

Answer:

Trigonal planar

Explanation:

Everything is connected to our central atom 'I'.

Iodine has 3 bonds around it: 1 single bond and 2 double bonds.

This 3 bonds will make a trigonal planar, hence the prefix 'tri' in the name (tri stands for the number 3).

The chart of given following ion is

Protons Electrons Neutrons

1) 6 2 8

2) 6 2 7

3) 8 10 9

4) 8 10 8

Simply put, a subatomic particle is a particle that is smaller than an atom. Protons, electrons, and neutrons are the three subatomic particles that may typically be separated from an atom.

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Answer

By adding water (H2O)

Explanation

In this reaction, water is a product, adding the product will favour the reverse reaction, which is the formation of more Co(H2O)6^2+.