how many electrons are in 40 Ne?

A 28.0 g sample of iron‑59 to decay to 1.75 g would take 176 days if its half-life is 44 days.

From the first order kinetics, We know that

t= 2.303 × log A₀[tex]A_{t}[/tex]     ....  (1)

Here, t is the number of days it would take for the sample to decay.

K refers to the first-order rate constant,

A₀ refers to the concentration at time = 0

[tex]A_{t}[/tex] is the concentration at time t.

Given that,

Half-life of the iron-59, [tex]t_{\frac{1}{2}}[/tex] = 44 days

A₀ = 28 g

[tex]A_{t}[/tex] = 1.75 g

t =?

K =?

In order to find the rate constant use the formula

[tex]t_{\frac{1}{2}}[/tex] = 0.693/K

K = 0.693 / [tex]t_{\frac{1}{2}}[/tex]

= 0.693/44

= 0.01575 per day

Substitute all the values in (1), to get,

t = (2.303/0.01575)×log(28/1.75)

= 176.06 days

Therefore, for a 28.0 g sample of iron‑59 to decay to 1.75 g, would take 176 days.

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The example of Iodine and tellurium where iodine which had lesser atomic mass was placed before tellurium proved that order of the Periodic table based on atomic mass was not always correct.

The periodic table as designed by Mendeleev was arranged such that the elements were arranged in order of increasing atomic mass.

However, in this case of tellurium and iodine, Mendeleev placed tellurium before iodine even though it had a greater atomic mass than iodine. This was because Mendeleev observed that elements with similar chemical properties were occurring in a regular pattern in the periodic table and iodine has similar chemical properties to bromine and chlorine before it.

Therefore, the case of Iodine and tellurium proved that arranging elements in the periodic table in order of increasing atomic mass was not always correct.

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Answer:

literally all you have to write to get the mark is the word isotopes

An aspect of the kinetic-molecular theory and can be used to explain the behavior of plasmas is particle exchange energy through elastic collision.

In physics, an elastic collision is an encounter (collision) between the two bodies in which the total kinetic energy of the two bodies remains the same. In an ideal, perfectly elastic collision, there is no net conversion of the kinetic energy into other forms such as heat, noise, or potential energy.

During collision of small objects, kinetic energy is first converted to potential energy associated with a repulsive or attractive force between the particles (when the particles move against this force, i.e. angle between the force and the relative velocity is obtuse), then this potential energy is converted back to kinetic energy (when the particles move with this force, i.e. angle between force and the relative velocity is acute).

Collisions of the atoms are elastic, for example Rutherford backscattering.

A useful special case of the elastic collision is when the two bodies have equal mass, in which case they will simply exchange their momenta.

The molecules—as distinct from atoms—of gas or liquid rarely experience perfectly elastic collisions because kinetic energy is exchanged between the molecules’ translational motion and their internal degrees of freedom with each collision. At any instant, half collisions are, to a varying extent, inelastic collisions (the pair possesses less kinetic energy in their translational motions after the collision than before), and half could be described as “super-elastic” (possessing the more kinetic energy after the collision than before). Averaged across the entire sample, the molecular collisions can be regarded as essentially elastic as long as Planck's law forbids energy from being carried away by black-body photons.

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Cells communicate via chemical signals which bind to specialized molecules on the plasma membrane surface. These molecules are called receptor proteins.

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Answer: I hope this helps.

Explanation:

At 15 °C, benzene has a density of 0.8787 g/ml. 131.8g make up 0.15 L of benzene's mass.

Density, mass of a unit volume of the material substance. The formula for density is d = M/V, where d is the density, M is mass, and V is volume. Density is commonly expressed in the units of grams per cubic centimeter. For example, the density of water is 1 gram per cubic centimeter, and the Earth’s density is 5.51 grams per cubic centimeter.

Density can also be expressed as the kilograms per cubic meter (in meter-kilogram-second or SI units). For example, the density of the air is 1.2 kilograms per cubic meter. The densities of common solids, liquids, and gases are listed in the textbooks and handbooks.

Density offers a convenient means of obtaining mass of a body from its volume or vice versa; the mass is equal to the volume multiplied by the density (M = V*d), while the volume is equal to the mass divided by the density (V = M/d). The weight of a body, which is usually of more practical interest than its mass, can be obtained by multiplying mass by the acceleration due to gravity.

There is a relationship between a substance's mass (m), volume (V), and density (d) that reads as follows:

d = m / V.

d = 0.8787 g/ml.

V = 0.15 x 1000 = 150 ml.

∴ the mass of 0.15 L of the benzene = d x V = (0.8787 g/ml) (150 ml) = 131.8 g.

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The amount of CO2 is produced is 60.28 g

In this combustion reaction , O2 act as a limiting reagent

96.0 g O2 = 3.0 mol O2 is present for the combustion reaction.

In the combustion reaction 60.4 g of water is formed

60.4 g of Water = 60.4 g * 1 mol / 18 g = 3.35 mol

3.35 mol of H20 has 6.32 mol of H atoms.

If hydrocarbon acts like limiting reactant , then 35.5 - 6.32 g of carbon = 29.18 g that is equal to 2.12 mol.

2.12 mol of C requires 2.12 mol * 2 = 4.24 mol of atoms to burn completely O atoms.

3.35 mol of H2O atom + 4.24 of O atoms = 7.59 mol. So, O2 is a limiting reactant.

3.35 mol of O2 atoms are in H2O , 6 - 3.35 = 2.65 mol of O2 atoms are there in CO2. Hence 1.37 mol of CO2 is going to produced.

Mass of CO2 produced = 1.37 * 44 = 60.28 g

By the law of conservation mass we found that 19.13 g of hydrocarbons remains unburnt.

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Answer:

0.350cm³

Explanation:

to obtain volume, divide density by

3.1÷8.86

0.350ml

1ml=1cm³

0.350ml=0.350cm³

In the day time the ocean absorbs the sunlight which is coming from the sun and at the night time the sun is not present so then the ocean releases that warmness.

The heat that the ocean absorbs is blended with the lower water quickly. That blending spreads the heat round. At night, at the same time as the land cools off quickly, the water on the surface is saved hotter because the water is mixed round with the hotter water underneath.

It is courtesy of the ocean breeze effect. countrywide weather service meteorologist Walter Drag explains that it takes place due to the distinction among the warm air over land and funky air soaring over the ocean .

So we can conclude that in the day time the ocean absorbs the sunlight which is coming from the sun and at the night time the sun is not present so then the ocean releases that warmness.

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The wavelength of blue light is 0.00000045 m. This wavelength in scientific notation is 4.5 × 10⁻⁷m.

A waveform signal that is carried in space or down a wire has a wavelength, which is the separation between two identical places adjacent crests in the consecutive cycles.

A spectrum is the term used to describe the range of wavelengths or frequencies for wave phenomena. The term was originally used to describe the electromagnetic spectrum, but it is now used to describe the sound spectrum and vibration spectrum.

The wavelength, which will also apply to troughs, is the separation between two wave crests. The frequency is measured in cycles per second and represents the number of vibrations that pass over a certain area in one second (Hz).

Thus,  This wavelength in scientific notation is 4.5 × 10⁻⁷m.

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The additional information needed to calculate the molality of a 7.35 molar solution of a non-electrolyte solid dissolved in water is the density of that solid.

To calculate the molality(m) from the molarity(M) of a solution, the following formula is used

m = 1000M/M x MM- 1000d

Here MM is the molar mass of solute

And d is the density of the solute

As the other information like molarity and molar mass of the solute is already given to us, the additional information needed is density.

Thus, the additional information needed to calculate the molality of a 7.35 molar solution of a non-electrolyte solid dissolved in water is the density of that solid.

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The concentration of 250cm³ of a sodium chloride solution that has a mass of 11.70g is 0.8M.

The concentration or molarity of a solution can be calculated by dividing the number of moles by its volume as follows:

Concentration = no of moles ÷ volume

According to this question, 250cm³ of a sodium chloride solution has a mass of 11.70g. The concentration of the solution can be calculated as follows:

Molar mass of NaCl = 58.5g/mol

moles of NaCl = 11.70g ÷ 58.5g/mol = 0.2mol

Concentration = 0.2mol ÷ 0.250dm³

Concentration = 0.8M

Therefore, the concentration of 250cm³ of a sodium chloride solution that has a mass of 11.70g is 0.8M.

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Answer:

C

Explanation:

The mass of KHP that was dissolved in 50.00 mL of the standardization titrant is 0.5634 g.

1 mol of KHP reacts with 1 mol of NaOH, which would mean that the amount of NaOH used is equal to the amount of KHP in the sample. We can use this to calculate the number of moles:

c = n/V, so n = c * V = 0.049 M * 0.025 L = 0.001225 mol of NaOH and KHP

Using this amount, we can then calculate the KHP moles in the sample of the standardization titrant:

22.20 mL : 0.001225 mol = 50.00 mL : X

X = 0.001225 mol * 50.00 mL / 22.20 mL = 0.002759 mol

Then, by using the M value of KHP (204.22 g/mol), we obtain the mass of KHP of the sample:

n = m/M, so m = n * M = 0.002759 mol * 204.22 g/mol = 0.5634 g

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5.0 ml of 0.10 m solution of Naoh is added to 30. ml of buffer solution of acetic acid (0.093m) and sodium acetate (0.12 m), then the pH of the solution is 4.72

CH3COOH +H2O → H3O+ + CH3COO-

ka = [H3O+] {CH3COO-] / [CH3COOH] [H2O]

⇒ [H3O+] = ka X [CH3COOH] / [CH3COO-] → 1

Let us consider the concenration of H3O+ at equilibrium = x

Thus, putting the values in equation 1

[H3O+] = ka X [CH3COOH] / [CH3COO-]

x = (1.8X 10^-5 X 0.00329) / (0.0031)

⇒ x = 1.91 X 10^-5

since x is the equilibrium concentration of H3O+, SO

equilibrium concentration of H3O+ = 1.91X 10^-5

Then pH = -log10 {H3O+}

= -log10{1.91 X 10^-5}

=4.72

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Answer:

combining two or more substances, such that each maintains its chemical identity. In other

At the end of the experiment you will be assessing the purity of your aspirin by measuring its absorbance at 525 nm. If the absorbance measurement is found to be 0. 040 then the % salicylic acid impurity in your aspirin will be 7.8 percent.

The sample solution's absorbance (A), as specified in the question, is 1.07. Beer's law is applied to determine the aspirin concentration, which is A = ebc.

Here, e is the extinction coefficient, which, according to the standard value for salicylic acid, is equal to 139.322 M-1cm-1, and b is the path length, which is equal to 1 cm. Now that we have our values,

A = ebc

c = A / (eb)

c = 1.07 / (139.322 × 1)

c = 0.00768 M

It is now necessary to compare the value of concentration determined with the concentration of aspirin previously given in order to calculate the percent salicylic acid in the sample.

Aspirin's initial concentration, which is specified in the query, is 0.02 grammes. Aspirin has a molar mass of 240 g/mol.

Consequently, the aspirin molecules will be,

0.02 / 240 = 8.33 × 10^-5 moles  

The final volume of the diluted solution given is 10 ml or 0.01 liters.  

The molarity of aspirin in the diluted solution will be,  

c1 = 8.33 × 10^-5 / 0.01 = 8.33 × 10^-3 M or 0.00833 M

Now, the percent of salicylic acid in the product will be,  

c1 - c / c1 × 100

(0.00833 - 0.00768) / 0.00833 × 100 = 7.8 %

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The question that a scientist can develop a testable hypothesis is as follows: Do all kinds of wood float in water? (option C).

A hypothesis is a tentative conjecture explaining an observation, phenomenon or scientific problem that can be tested by further observation, investigation and/or experimentation.

The construction of hypothesis is a vital component of any experiment, which must be testable.

However, prior to the construction of hypothesis, a scientific question must be asked.

According to this question, the question that a scientist can develop a testable hypothesis is as follows: Do all kinds of wood float in water? The testable hypothesis will be to use different wood on water.

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Carbon plays a fundamental role in the structure of organic compounds.

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The forces to which limestone must be exposed to in order to change into marble is (c) heat and pressure.

Limestone has calcium carbonate in it. So, the chemical formula for this is CaCO₃. When it is burnt it gives lime. It is a sedimentary rock.

Sedimentary rocks are those rocks which are formed from deposition of already existing rocks of fossils on the surface of the earth.

Marble also has calcium carbonate in it. So, the chemical formula for this is also CaCO₃. It is a metamorphic rock.

Metamorphic rocks are formed when they have to face harsh conditions like heat and pressure etc.

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200 sec or 3 min 20 msec

we need to get to class, 300 meters away,

so the distance becomes = 300 m

we can only walk in the hallways at about 1.5m/s

so the time become = 1.5m/s

time will it take to get to our class

time = distance/speed

time = 300/1.5

time = 200 sec or 3 min 20 msec

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The potential energy for a mass on a spring is proportional to the square of  Displacement.

Potential energy is present  in a spring is because applying a force to deform a spring.

The elastic potential represented by U and S.I unit is J

Elastic potential energy is given by:

U = 1/2 kx²

The elastic potential energy is directly proportional to the square of the change in length or displacement and spring constant.

k is spring constant

x is the displacement

as x increases potential energy increases.

Thus, The potential energy for a mass on a spring is proportional to the square of  Displacement.

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1.06 atm

A sample of gas at STP,

what will be  the final pressure if the temperature is heated to 45°C and

the volume remains constant.

as per above statement , we got

pressure = 1 atm

volume = v

temperature = 298 k ( k stands for kelvin)

now, we have to find the final pressure as temperature increases to 318 kelvin and volume remain sames.

so, now, by applying ideal gas equation,

PV = nRT

here n and R is constant , so we neglect it,

now equation become

P1V/T1 = P2V/T2

Now, putting all the values

1/298 = p2/318

p2 = 318/298

p2 = 1.06 atm

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Considering the ideal gas law, to a temperature of 1088.85 K or 815.85°C must 0.588 moles of NH3 gas have to be heated in a 15.0 L container in order for it to exert a pressure of 3.50 atm.

Ideal gases are a simplification of real gases that is done to study them more easily. It is considered to be formed by point particles, do not interact with each other and move randomly. It is also considered that the molecules of an ideal gas, in themselves, do not occupy any volume.

An ideal gas is characterized by three state variables: absolute pressure (P), volume (V), and absolute temperature (T). The relationship between them constitutes the ideal gas law, an equation that relates the three variables if the amount of substance, number of moles n, remains constant and where R is the molar constant of gases:

P×V = n×R×T

In this case, you know:

Replacing in the definition of ideal gas law:

3.50 atm× 15 L= 0.588 moles×0.082 [tex]\frac{atm L}{mol K}[/tex]×T

Solving:

(3.50 atm× 15 L)÷ (0.588 moles×0.082 [tex]\frac{atm L}{mol K}[/tex])= T

1088.85 K= 815.85 C= T (being 273 K= 0 C)

Finally, to a temperature of 1088.85 K or 815.85°C must 0.588 moles of NH3 gas have to be heated in a 15.0 L container in order for it to exert a pressure of 3.50 atm.

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Answer:

How much matter something has

Density is how much matter something has.

The amount per unit of length, area, or volume: as. a: a substance's mass per unit volume. the distribution of a quantity per unit, typically of space, such as mass, power, or energy.

A substance's density is defined as its mass per unit of volume. Density is most frequently represented by the symbol, however Latin letter D may also be used. Mass divided by volume is the formula for density in mathematics: display style rho = frac mV. where m is the mass, V is the volume, and is the density.

The ratio of an object's mass to its volume is its density.

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Anhydrous sodium sulphate is a common inert drying agent used in laboratories to get rid of any remaining water vapor in organic solutions. Therefore, it is needed in this experiment.

It is more effective yet takes longer to work than the same substance, magnesium sulphate. Sodium sulphate is a drying agent.

The fact that it is a fine powder with a lot of surface area makes it a fast-drying agent. Sodium sulphate (n=10, e=25 mg/L) is primarily used for very wet solutions and has a very high capacity.

It absorbs other polar substances like alcohols, etc., but it is particularly effective in ethereal solutions.

Although it has numerous additional uses, sodium sulphate is primarily employed in the production of detergents and in the Kraft process of paper pulping.

The decahydrate’s natural mineral form, mirabilite, accounts for about half of the world’s output, with the other half coming from chemical byproducts.

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When the base sodium hydroxide dissolves in water, sodium and chloride ions are formed.

Any material that is slippery to the touch, tastes unpleasant, alters the colour of indicators (such as turning red litmus paper blue), combines with acids to generate salts, and facilitates certain chemical processes is considered a base in chemistry (base catalysis).

When the base sodium hydroxide dissolves in water, sodium and chloride ions are formed.

Since sodium hydroxide is an inert solid in itself, its ions do not impart any colour to the solution when it dissolves in water. So, a colourless solution is produced when sodium hydroxide is added to water.

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