Is the reaction mg²⁺(aq) + h₂o(l) → mgo(s) + 2h⁺(aq) endothermic or exothermic?

By applying Charles's law - V1/T1 = V2/T2 - and rearranging the formula as V2 = V1*(T2/T1), we find that the final volume of the argon gas when the temperature is raised to 42°C under constant pressure is 5.91 L.

This question deals with the application of Charles's law, a fundamental concept in gas laws. Charles's law states that the volume of a gas is directly proportional to its temperature in Kelvin, assuming that pressure and the amount of gas remain constant.

First, convert the temperatures provided from Celsius to Kelvin. So, T1 = 15°C + 273 = 288 K and T2 = 42°C + 273 = 315 K. For the calculation, you would apply Charles's law formula - V1/T1 = V2/T2. Here, V1 is the initial volume (5.40 L), and T1 is the initial temperature in Kelvins (288 K). T2 is the final temperature in Kelvins (315 K), and we have to find V2 which is the final volume.

By rearranging the formula we get V2 = V1*(T2/T1) = 5.40 L * (315 K / 288 K) = 5.91 L.

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The claim that only an odd number of orbitals is possible for any electron sublevel is incorrect. There can be both odd and even numbers of orbitals, such as 1 orbital in the s subshell and 3 in the p subshell.

The statement that 'only an odd number of orbitals is possible for any electron sublevel' is not accurate according to quantum theory and the rules for assigning electrons to orbitals. In atomic structure, orbitals are spaces where electrons are likely to be found. These orbitals come in various shapes (s, p, d, f) and each type has a specific number of orbitals that can contain electrons. According to the Pauli Exclusion Principle, an orbital can hold a maximum of two electrons with opposite spins. Therefore, the s subshell has 1 orbital for 2 electrons, the p subshell contains 3 orbitals for up to 6 electrons, the d subshell consists of 5 orbitals for up to 10 electrons, and the f subshell has 7 orbitals for up to 14 electrons. This shows that the number of orbitals in a sublevel can be both even and odd.

For example, the electron configuration for fluorine is 1s² 2s² 2p⁵, illustrating how electrons fill into s and p orbitals. Furthermore, Hund's rules dictate that electrons are added to sublevels with every orbital singly occupied before any orbital is doubly occupied, reflecting the conservation of orbitals in quantum mechanics.

Answer:

it is c

Explanation:

The solution is not a pure substance because it is a mixture between a solute and a solvent. Therefore, option (C) is correct.

Pure substances can be described as elements that cannot be broken down into simple substances that contain only one kind of atom in the whole composition.

A pure substance can be described as made up of two or more chemical elements that are chemically combined and has a set composition such type of pure substance is called a compound. For example, water is a pure compound that is composed of hydrogen and oxygen in a whole ratio of 2:1.

A mixture can be described as made up of two or more different substances which are only physically combined but not chemically. A mixture can be separated into its original components.

The composition of a heterogeneous mixture does not have uniform throughout the mixture while the composition in a homogeneous mixture is always the same.

Therefore, the solution is a mixture, not a pure substance.

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All isotopes of an element have the same number of protons and different numbers of neutrons. So, the isotopes Oxygen-16, Oxygen-17, and Oxygen-18 have different numbers of neutrons, not protons or electrons.

The three isotopes, Oxygen-16, Oxygen-17, and Oxygen-18, are all isotopes of the element Oxygen. This means that they have the same number of protons, as the number of protons determines the identity of an element. In this case, Oxygen isotopes all have 8 protons. However, isotopes of the same element can have different numbers of neutrons. Indeed, Oxygen-16, Oxygen-17, and Oxygen-18 have 8, 9, and 10 neutrons respectively. They also have an identical number of electrons as protons to make the atom electrically neutral.

So, the statement 'They have different number of neutrons' is the correct one among the options.

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Answer:

The correct answer will be- low power objective lens.

Explanation:

In a light microscope, two types of lenses are used:

1. Ocular lens- the lens near to the eye of a viewer

2. Objective lens- The lens near the object.

Since the field of view decreases with increasing the objective power of the lens, therefore one wants to observe the large field of view than one should use low power of objective lens that is 4x.  

Thus, the low power objective lens is the correct answer.

The molar mass of the unknown gas is 92.0 g/mole

Explanation:

Part a in an effusion experiment, it was determined that nitrogen gas, n2, effused at a rate 1.812 times faster than an unknown gas. what is the molar mass of the unknown gas? express your answer to four significant figures and include the appropriate units.

The molar mass is the mass of a sample of that compound divided by the amount of substance in that sample in moles. Molar mass and molecular weight are often confused, but their values are very different.

Graham's law states the rate of diffusion or of effusion of a gas is inversely proportional to  its molecular weight of the square root .

Graham's Law = rate of effusion of gas 2  / rate of effusion of gas 2

Graham's Law = square root (MM1 / MM2), where MM1 and MM2 are the molar masses of the gases.  

Gas_2 = N_2, therefore

1.812 =  √ (MM_1 / MM N_2)

1.812 = √ (MM_1 / 28.0)

1.812 = √ (MM_1 / √ 28.0 )

1.812 = √ (MM_1 / 5.29 )

1.812 x 5.29 = √ MM_1 = 9.59

MM_1 = 9.59^2 = 92.0 g/mole

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Answer: This is known as non-polar covalent bond.

Explanation:

A covalent bond is formed when sharing of electrons takes place between the atoms forming a bond.

A polar covalent bond is formed when the atoms forming a bond have significant difference in electronegativities. This leads to the formation of poles in the atoms. For Example: HCl

A non-polar covalent bond is formed when the atoms forming a bond dpes not have significant difference in electronegativities or have similar electronegativity. For Example: [tex]H_2[/tex]

Hence, the bond is known as non-polar covalent bond.

Final answer:

The indication of a chemical change is the transformation of one substance into another, which is represented by option C) Change in the type of substance present. It involves observable signs like temperature change, color change, light production, gas formation, and precipitate formation.

Explanation:

What indicates a chemical change is a fundamental concept in understanding reactions and transformations in chemistry. The correct answer to the student's question is C) Change in the type of substance present. This occurs when a substance is turned into another as a result of a chemical reaction. Such changes are typically hard to reverse.

Observations that help indicate a chemical change include temperature changes, light given off, unexpected color changes, formation of bubbles that aren't due to boiling, and the formation of a precipitate. A change from a liquid to a gas or a change in texture, for example, can be attributed to physical changes, which do not alter the substance's molecular composition. The student's question relates to identifying chemical changes, focusing specifically on transformations that result in new substances with different chemical properties.

Assuming that the reaction is unimolecular on both reactant and product sides such that:

HA  +  OH-   -->  A-  +  H2O

Therefore the amount of A- left is:

mmol HA = 9.00 - 3.00 = 6.00 
mmol A- = 3.00 

pKa = - log Ka = 5.25 

Calculating for pH:
pH = 5.25 + log 3.00/6.00

To calculate the resulting pH of a solution made by mixing 9.00 mmol of HA and 3.00 mmol of a strong base, you need to determine the concentrations of the acid and base, calculate the concentration of the resulting solution, find the pOH using the concentration of the conjugate base, and finally convert the pOH to pH.

The pH of the solution can be calculated using the concentrations of the acid and the base. We can assume that the strong base reacts completely with the acid, so the resulting solution will contain only the conjugate base and water. Since we know the concentrations of the acid and base, we can determine the moles of each and calculate the new concentrations of the resulting solution. Finally, we can use the concentration of the conjugate base to find the pOH and then convert it to pH.

Given:
moles of HA = 9.00 mmol
moles of strong base = 3.00 mmol
Total volume of solution = unknown

Let's assume the total volume of the solution is 1 L for easier calculations. The concentration of the acid (HA) is 9.00 mmol / 1 L = 9.00 mM. The concentration of the conjugate base (A-) is also 9.00 mM since the acid and base react in a 1:1 ratio. The pOH of the solution can be calculated using the concentration of the base:

pOH = -log([OH-])
Since the concentration of the base is 9.00 mM, the pOH = -log(0.009) = 2.05

The pH of the solution can be calculated by subtracting the pOH from 14:
pH = 14 - pOH = 14 - 2.05 = 11.95

Therefore, the resulting pH of the solution is approximately 11.95.

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Answer:- The limiting reactant is HCl.

Explanation: The balanced equation is:

[tex]2HCl+Ca\rightarrow CaCl_2+H_2[/tex]

It's a stoichiometry problem. Masses of both the reactants are given and the questions asks to find out the limiting reactant.

We convert the given grams of each reactant to moles on dividing by its molar mass. Now, we can calculate the moles of any of the product on multiplying the moles of the reactant by mole ratio.

We do this starting with both the reactants and see which one gives less number of moles of the product. The limiting reactant is the one giving least number of moles of the product.

Molar mass of HCl is 36.46 gram per mol and that of Ca is 40.08 gram per mol.

Let's say we calculate the moles of hydrogen gas produced in the reaction. Mole ratio of [tex]H_2[/tex] to HCl is 1:2 and the mole ratio of [tex]H_2[/tex] to Ca is 1:1 .

The calculations are as shown below:

[tex]100gHCl(\frac{1molHCl}{36.46gHCl})(\frac{1molH_2}{2molHCl})[/tex]

= 1.37 mol [tex[H_2[/tex]

[tex]100gCa(\frac{1molCa}{40.08gCa})(\frac{1molH_2}{1molCa})[/tex]

= 2.50 mol [tex]H_2[/tex]

From above calculations, we get the least moles of hydrogen gas from 100 grams of HCl. So, the limiting reactant is HCl.

Hertz extended Maxwell’s idea that light is produced by the interaction of electric and magnetic fields.

Answer:

Hertz extended Maxwell’s idea that light is produced by the interaction of electric and magnetic fields.

Explanation:

According to Maxwell electromagnetic waves propagated perpendicular to the direction of the oscillating mutually perpendicular electric and magnetic field. This electromagnetic disturbance could move through vacuum with the speed of light and had wave like properties.

Hertz designed experiments which proved Maxwell's idea: the electromagnetic nature of light.

Final answer:

To determine the number of moles of nitrogen in 1.61 x 10²⁴ nitrogen particles, divide by Avogadro's number, resulting in 2.673 moles of nitrogen.

Explanation:

The student is asking about the number of moles of nitrogen contained in a given number of nitrogen particles. To find this, we use Avogadro's number, which is the number of particles in one mole of a substance. The value of Avogadro's number is 6.022 x 10²³ mol−1. Since the question indicates that there are 1.61 x 10²⁴ nitrogen particles, we divide this number by Avogadro's number to determine the moles.
Here's the calculation:
Number of moles (n) = Number of particles (N) / Avogadro's number (NA)
n = 1.61 x 10²⁴ particles / 6.022 x 10²³ mol−1
n = 2.673 moles of nitrogen

The formula relating the sample variance, SS and n can be written as:

sample variance = SS / (n – 1)

so let us take that:

SS = 40

n = 5

calculate variance using the formula:

sample variance = 40 / (5 – 1)

sample variance = 10

Therefore the answer is:

False

Answer:

c. Einstein

Explanation:

Einstein is most credited  with the idea that a quantum of light (photon) can act as a particle. He proposed that light behave as photons or  quantum of energy and used it to explain the Photoelectric Effect for which he received the Noble prize. Prior to that light was believed to behave as a wave or electromagnetic radiation only. However, photoelectric effect showed that light has particle nature as well.

Copper, silver, mercury, and gold are less reactive than hydrogen as they are positioned at the bottom of the activity series and do not readily react with acids to produce hydrogen gas.

The metals listed that are less reactive than hydrogen (H2) are those found at the bottom of the activity series. Specifically, these metals include copper (Cu), silver (Ag), mercury (Hg), and gold (Au). These metals do not react with acids to form hydrogen gas and hence are considered less reactive than hydrogen. Additionally, in the context of the electrochemical series, these metals are known as inert metals, indicating their low reactivity and their position at the very bottom of the activity series. Therefore, they do not readily corrode in the presence of dilute acids.

It's important to note that aside from basic trends, the exact order of reactivity of metals can be determined from the activity series or electrochemical series, where the lower a metal's position relative to hydrogen, the less reactive it is in comparison.

The mass number of the atom is 45.

Given:

An atom contains 21 electrons, 21 protons, and 24 neutrons.

To find:

The mass number of an atom.

Solution:

Number of protons in atom = p = 21

Number of neutrons in atom = n = 24

Mass number of an atom = A

[tex]A = p + n \\\\A = 21 + 24 \\\\A = 45[/tex]

The mass number of the atom is 45.

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Its dune. The Delta landform is involving water, not sand. Dunes are basically sand, so i would pick dune

Answer:

Argon ( Ar)

Explanation:

For a 0.28M HCl solution, the concentration of H3O+ ions is assumed to be 0.28M due to the full ionization of strong acid. OH- concentration is obtained from the ion-product of water, and the pH is calculated from the negative log of H3O+ concentration.

The concentration of hydronium ions [H3O+] in a 0.28M solution of HCl, a strong acid, can be assumed to be 0.28M. This is due to the complete ionization of a strong acid.

The OH- concentration [OH-] can be obtained from Kw, the ion-product of water (1x10^-14 at 25 degree Celsius). Knowing [H3O+] and Kb, we can calculate [OH-] using this relationship: [H3O+].[OH-] = Kw. The pH is then calculated from the [H3O+] using the relationship pH = -log([H3O+]).

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Final answer:

A hydrogen bond is a weak attraction between the slightly positive hydrogen end of one polar molecule and the slightly negative end of another, while a covalent bond is a strong bond involving the sharing of electrons between atoms within a molecule. Hydrogen bonds are depicted with dashed lines and covalent bonds with solid lines in molecular diagrams. The hydrogen bond is much weaker than a covalent bond, requiring significantly less energy to break.

Explanation:

The key difference between a hydrogen bond and a covalent bond is the nature of the interactions that hold atoms or molecules together. In a water molecule ([tex]H_{2}[/tex]O), the oxygen and hydrogen atoms are held together by covalent bonds, which involve the sharing of electrons between atoms and are depicted by solid lines in molecular diagrams. These bonds are quite strong because they involve the sharing of electrons to create a stable electron configuration around each atom.

In contrast, a hydrogen bond is a weak attraction between the slightly positive hydrogen end of one polar molecule and the slightly negative end of another polar molecule, such as the oxygen atom in a different water molecule. This interaction is depicted by dashed lines in molecular diagrams and does not involve electron sharing; instead, it's a result of polar covalent bonds within the molecules that create slight positive and negative charges leading to an attraction between molecules. Because hydrogen bonds are between molecules, they are much weaker than the covalent bonds within molecules, requiring only about 10% of the energy to break compared to typical covalent bonds. This behavior illustrates why we can boil water, breaking the hydrogen bonds, without breaking the water molecules themselves, which would require disrupting their covalent bonds.