How do you determine the frequency of light whose wavelength is 4.257x10^-7?

Final answer:

The complete ionic equation for the neutralization of HCl by NaOH is Na+ + OH- + H+ + Cl- → H2O + Na+ + Cl-. The net ionic equation, omitting the spectator ions Na+ and Cl-, is H+ + OH- → H2O.

Explanation:

The total ionic equation for the neutralization reaction between sodium hydroxide (NaOH) and hydrochloric acid (HCl) is written as:

Na+ (aq) + OH− (aq) + H+ (aq) + Cl− (aq) → H₂O(l) + Na+ (aq) + Cl− (aq)

In this reaction, the Na+ and Cl− ions are spectator ions and do not participate in the actual neutralization. Thus, the net ionic equation, which shows the actual chemical change, is simply:

H+ (aq) + OH−(aq) → H₂O(l)

Here, the hydrogen ion (H+) from the acid reacts with the hydroxide ion (OH−) from the base to form water (H₂O), which is the only non-ionic product.

The moles of [tex]\rm Cl_2[/tex] needed to have stoichiometrically equivalent amounts of Na and [tex]\rm Cl_2[/tex] is 1.5 moles.

Stoichiometrically equivalent is defined as a definite quantity of one substances reacted with the definite quantity of other substances represented in the equation.  

It can also be defined as the relationship between the quantities of reactant and product before, during and following equation.

The ratio of [tex]\rm NaCl_2[/tex] is 1:2 because in [tex]\rm NaCl_2[/tex] there is only one mole Na ion is present and 2 mole of Cl ion is present.

Thus moles of Na present = 3 moles

So, 2 / 1 = 3 / x

     x = 3 / 2

     x = 1.5 moles

Thus, the moles of [tex]\rm Cl_2[/tex]needed to have stoichiometrically equivalent amounts of Na and[tex]\rm Cl_2[/tex] is 1.5 moles.

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Answer:false

Explanation:

Answer:

-283 KJ, exothermic

Explanation:

We are given that

Enthalpy of a mixture of a gases reactants

Change in enthalpy=[tex]\Delat H[/tex]=-228 KJ

Where negative sign represents the enthalpy decreases.

Pressure=Constant.

Work don=w=-55 KJ

We have to calculate the change in energy of the gas mixture during the reaction.

At constant pressure, the change in enthalpy

[tex]\Delta H=\Delta U+P\Delta V[/tex]

Where w=[tex]-P\Delta V[/tex]

Where P=Constant

[tex]\Delta V=[/tex] Change in volume

[tex]\Delta U=[/tex] Change in energy

[tex]\Delta U=\Delta H-P\Delta V[/tex]

[tex]\Delta U=\Delta H+w[/tex]

Substitute the values then we get

[tex]\Delta U=-228-55=-283[/tex] KJ

Hence, the change in energy of the gas mixture during the reaction=-283 KJ

Change in enthalpy is negative it means the reaction is exothermic because the energy is evolved.

The reaction is exothermic, heat is evolved.

From the first law of thermodynamics we know that energy is neither created nor destroyed.

Therefore, the change in energy is obtained from the formula;

ΔU = ΔH + w

ΔU = change in energy

ΔH = Change in enthalpy (heat absorbed or evolved)

w = work done

ΔU = ?

w =  -55kJ

ΔH = -228. kJ

ΔU= -228. kJ + ( -55kJ)

ΔU = -283 kJ

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Answer:

A)  ⁴He₂

Explanation:

²³⁸U₉₂ → ²³⁴Th₉₀ + A

To obtain the missing element (A), we have to first find it's atomic and mass numbers.

The mass number is the sum total of the protons and neutrons in an atom. It is usually equal to the superscript in an atom. for example in ²³⁸U₉₂ the mass number is 238.

The atomic number is the total of the protons in an atom. It is usually equal to the subscript in an atom. for example in ²³⁸U₉₂ the atomic number is 92.

In a chemical eqation, there's conservation of mass.

With this, mass number of products = mass number of reactants. same thing for the atomic number.

Mass number of Product = 238

Mass number of Reactant = 234 + x

238 = 234 + x

x = 238 - 234 = 4

Atomic number of product = 92

Atomic number of reactant = 90 + y

92 = 90 + y

y =  92 -90 = 2

So the atomic number of the missing element is 2 and its mass number is 4.  ⁴A₂.

Among the elements, the only match is  ⁴He₂. So the correct option is A

Answer: The speed of the car is 17.4 m/s

Explanation:

Speed is defined as the ratio of distance traveled to the time taken.

Mathematically,

[tex]\text{Speed}=\frac{\text{Distance traveled}}{\text{Time taken}}[/tex]

We are given:

Distance traveled = 112.6 km = 112600 m    (Conversion used: 1 km = 1000 m)

Time taken = 1.8 hr = [tex]1.8\times 3600=6480s[/tex]     (Conversion factor: 1 hr = 3600s)

Putting values in above equation, we get:

[tex]\text{Speed of car}=\frac{112600m}{6480s}=17.4m/s[/tex]

Hence, the speed of the car is 17.4 m/s

Answer: 12 electrons

Explanation:

As the electrons move around the atom, they can move in any direction as long as they stay in their shell, and they are also constantly spinning. Shells or orbitals are specific distances from the nucleus and they are energy levels. Each of those shells has a name and there are a many ways that atomic shells are described.

First, the basic regions where electrons are found which is described using an "n" value, or the letters K, L, M, N, O, P, and Q. The "K" shell is the one closest to the nucleus, and "Q" is the farthest away. The second description looks at how electrons act inside of the shells, described with the "l" value which indicates in which suborbital an electron is found in (s, p, d, f, g, and h)

Quantum numbers are numbers associated with physical quantities conserved in certain quantum systems. 

So, L refers to the s subshell, so L=0 is related with the S-subshell. Ba is an atom found in the 6th shell, and it has the electronic configuration of [Xe]6s2 (1s2s2p3s3p4s3d4p5s4d5p6s), so there would be .12 electrons there because there are 6 s-orbitals with 2 electrons each. On the other hand, ml values rage from -L to L, and since the L value from this question is 0, there are no electrons that have both values of L=0 and ml=1. Since only one orbital of each type can have this magnetic quantum number and each orbital can host 2 electrons, we also have 12 electrons fitting this description.  

The mixing of enantiomers D and L yields a zero-degree observed rotation. Dilution of D with solvent maintains the same observed rotation, and also doesn't change the specific rotation.

Enantiomeric compounds D and L are mirror images of each other, thus they will rotate plane-polarized light equally but in opposite directions. Therefore, when these are mixed in equal volumes, the rotation of one enantiomer will cancel out the rotation of the other, resulting in an observed rotation of 0 degrees.

The solution's concentration is being halved when the solution of D is diluted with an equal volume of solvent. But, because the observed rotation is directly proportional to the path length and inversely proportional to the concentration, the observed rotation will remain the same at 0.20 degrees, because you're essentially doubling the path length while halving the concentration.

The specific rotation will stay the same i.e 0.20 degrees after the dilution in question c), because it is an intrinsic property of the substance D and does not change with concentration or path-length.

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Answer : The mass of iron metal needed are, 87.4 grams

Solution : Given,

Mass of Al = 150 g

Mass of [tex]Fe_2O_3[/tex] = 250 g

Molar mass of Al = 27 g/mole

Molar mass of [tex]Fe_2O_3[/tex] = 160 g/mole

Molar mass of Fe = 56 g/mole

First we have to calculate the moles of Al and [tex]Fe_2O_3[/tex].

[tex]\text{ Moles of }Al=\frac{\text{ Mass of }Al}{\text{ Molar mass of }Al}=\frac{150g}{27g/mole}=5.55moles[/tex]

[tex]\text{ Moles of }Fe_2O_3=\frac{\text{ Mass of }Fe_2O_3}{\text{ Molar mass of }Fe_2O_3}=\frac{250g}{160g/mole}=1.56moles[/tex]

Now we have to calculate the limiting and excess reagent.

The balanced chemical reaction is,

[tex]Fe_2O_3+2Al\rightarrow Al_2O_3+2Fe[/tex]

From the balanced reaction we conclude that

As, 2 mole of [tex]Al[/tex] react with 1 mole of [tex]Fe_2O_3[/tex]

So, 1.56 moles of [tex]Al[/tex] react with [tex]\frac{1.56}{2}=0.78[/tex] moles of [tex]Fe_2O_3[/tex]

From this we conclude that, [tex]Fe_2O_3[/tex] is an excess reagent because the given moles are greater than the required moles and [tex]Al[/tex] is a limiting reagent and it limits the formation of product.

Now we have to calculate the moles of [tex]Fe[/tex]

From the reaction, we conclude that

As, 2 mole of [tex]Al[/tex] react to give 2 mole of [tex]Fe[/tex]

So, 1.56 mole of [tex]Al[/tex] react to give 1.56 mole of [tex]Fe[/tex]

Now we have to calculate the mass of [tex]Fe[/tex]

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

[tex]\text{ Mass of }Fe=(1.56moles)\times (56g/mole)=87.4g[/tex]

Thus, the mass of iron metal needed are, 87.4 grams

Answer:

The correct answer is option B) It would sink directly to the bottom.

Explanation:

Hello!

Let's solve this!

Generally, solids have a higher density than liquids. In this case the densities are differentiated between the syrup, the oil and the water.

I think the solid would sink to the bottom.

After the explanation, we conclude that the correct answer is option B) It would sink directly to the bottom.

Iron occurs 8 valence electron and column 7 elements have 7 valence electrons that's why iron will not be kept in column 7.

The periodic table groupings are seen as vertical columns with numbers ranging from 1 through 18.

The count of electrons occupy in outermost orbital of the particular atom, can be introduced as valence electrons.

Such kind of elements which posses 7 valence electrons , will be placed in column 7. Iron has 8 valence electron but column 7 elements have 8 valence electron that's why iron will not be kept in column 7.

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When a 38 gram sample of water freezes it releases approximately 12.66 kJ of heat. This is because freezing is an exothermic process, meaning the substance releases energy in the form of heat.

The process of freezing water is exothermic, meaning it releases heat. The amount of heat released when water freezes can be calculated using its enthalpy change upon freezing. For water, the enthalpy change upon freezing is approximately -6.0 kJ/mol. Here's how to calculate:

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When a 38 gram sample of water freezes it releases approximately 12.66 kJ of heat.

This is because freezing is an exothermic process, meaning the substance releases energy in the form of heat

The formula to calculate the heat released is:

Given that: m = 38 grams and Lf = 334 J/g, we can plug in the values:

Therefore, 12.66 kJ of heat is released when a 38-gram sample of water freezes.

Correct question is: How much heat is released by a 38-gram sample of water to freeze at its freezing point?

The mass of platinum taken here is 338.9 g. The mass of one mole of platinum is 195 g. Then , number of moles in 338.9 g is 1.73.

Platinum is 78th element in periodic table. It is a transition metal in d -block. Platinum is a precious metal used in making of ornaments, electrical devices etc.

volume Pt = 15.8 cm³

density = 21.4 g/ cm³

mass = volume × density = 338.9 g.

Atomic mass of platinum = 195 g/mol.

The mass of one mole of platinum metal is 195 g. Then the number of moles in 338.9 g can be calculated as follows:

no.of moles = weight/ atomic mass

n = 338.9 g / 195 g/mol

  = 1.73 moles.

Therefore the number of moles of Pt is 1.73.

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Answer: The mass of mercury will be 20.15 g.

Explanation:

Density is defined as the mass contained per unit volume.

[tex]Density=\frac{mass}{Volume}[/tex]

Given : Mass of bromine = ?

Density of bromine= [tex]3.1g/ml[/tex]

volume of bromine = 6.5 ml

Putting in the values we get:

[tex]3.1g/ml=\frac{mass}{6.5ml}[/tex]

[tex]mass=20.15g[/tex]

Thus the mass of bromine is 20.15 g.

the answer is A. ionic

Ionic compounds produce more ions in solution than covalent compounds, as they dissociate into their constituent ions, resulting in a greater number of dissolved particles compared to the individual molecules of covalent substances.

In solution, ionic compounds tend to produce more ions than covalent substances. When ionic compounds like sodium chloride (NaCl) dissolve in water, they separate into their constituent ions - for instance, NaCl yields one mole of Na+ ions and one mole of Cl⁻ ions, resulting in twice as many particles per mole as there were originally in the solid state.

On the other hand, covalent compounds typically dissolve in water as individual molecules without forming ions, such as glucose (C₆H₁₂O₆), which results in the same number of particles as moles dissolved.

For example, one mole of an ionic compound like NaCl will produce 2 moles of dissolved particles (ions), which is greater than the 1 mole of particles that results when one mole of a covalent compound, such as glucose, dissolves. This means that ionic substances affect the properties of solutions more significantly compared to an equivalent amount of dissolved covalent substances.

Silicon dioxide (SiO₂), also known as silica, is a non-polar molecule.

A non-polar molecule is a molecule that has an even distribution of electrical charge, meaning it does not have a positive or negative end.

The molecule's geometry and symmetry lead to its non-polar nature. SiO₂ consists of one silicon atom bonded to two oxygen atoms, forming a linear structure. The oxygen atoms are positioned on opposite sides of the silicon atom, resulting in a symmetric arrangement.

As a result, the bond dipoles cancel each other out, resulting in a non-polar molecule overall.

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The correct options are as follows:

17. C.

Radioactive decay refers to the process by which an unstable atomic nucleus loses energy by giving out radiations. The radiations emit can be in form of alpha or beta particles or gamma rays. Radioactive decay is a random process, that is, one can not predict when it would happen. Radioactive decay occurs when the nucleus of an atom decay and no longer have enough binding energy to hold the atomic sub particles together.

18. B.

Radioactive decay occurs when the nucleus no longer have enough energy to hold the sub particles in the nucleus together. This situation always occur when there are excess protons or neutrons in the nucleus of the atom. In the nucleus of an atom, two forces are usually at work, nuclear and electrostatic forces. While proton experience both of these forces, neutron only experience the nuclear force. These two forces that are in opposition bring about radioactive decay.

Radioactive decay occurs when the nucleus of an atom decays. The correct answer is

Radioactive decay occurs due to the electric force and nuclear forces being in opposition to each other.

Radioactive decay involves the spontaneous transformation of unstable atomic nuclei into more stable configurations, resulting in the emission of particles or electromagnetic radiation.

Reasons

In an atomic nucleus, protons are positively charged particles, and they experience repulsive electric forces due to their like charges. However, nuclear forces, specifically the strong nuclear force, help hold the protons and neutrons together in the nucleus. When the balance between these forces is disrupted, such as when the nucleus becomes unstable, radioactive decay can occur as the nucleus seeks a more stable configuration.

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Final answer:

A common product of acid-base neutralization reaction is water and a salt.

Explanation:

A common product of acid-base neutralization reaction is water and a salt. In this reaction, an acid and a base react to form a salt and water. For example, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), the products are sodium chloride (NaCl) and water (H2O).

In the given question, Gamma rays consist of pure energy. The correct answer is option B.

Gamma rays are electromagnetic radiation with very high frequency and short wavelength.

They have no mass or charge, and are not considered particles like electrons, protons, or beta particles. Gamma rays are produced by the decay of atomic nuclei and are often associated with nuclear reactions such as those that occur in the sun, in nuclear power plants, or in nuclear weapons.

Therefore, Gamma rays are option B. "pure energy" in the form of electromagnetic radiation with an extremely high frequency and short wavelength.

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