In his explanation of the threshold frequency in the photoelectric effect, Einstein reasoned that the absorbed photon must have a minimum energy to dislodge an electron from the metal surface. This energy is called the work function (Ф) of the metal. What is the longest wavelength of radiation (in nm) that could cause the photoelectric effect in each of these metals:
(b) titanium, Фi=6.94 × 10⁻¹⁹J

Answer:

write the following as fractions in their simplest form

The correct statements are that a rock is considered an ore when it contains at least one metallic mineral in sufficient amounts to be extracted profitably and when it contains fluorite or sulfur minerals in sufficient amounts to be extracted profitably.

When it contains at least one metallic mineral in sufficient amounts to be extracted profitably.

When it contains fluorite or sulfur minerals in sufficient amounts to be extracted profitably.

Step-by-step explanation:

When it occurs in sufficient amounts to be used to build roads and buildings: This statement is incorrect. Rocks that are used for construction purposes, such as limestone or sandstone, are not considered ores unless they also contain economically valuable minerals.

Only when it contains lead: This statement is incorrect. Ores are not limited to containing only lead. Ores can contain various metallic minerals, not just lead.

When it contains at least one metallic mineral in sufficient amounts to be extracted profitably: This statement is correct. Ores are rocks that contain valuable metallic minerals in concentrations that make extraction economically feasible. These minerals can include gold, silver, copper, aluminum, zinc, and many others.

Only when it contains iron: This statement is incorrect. While iron ores are commonly known and widely used, ores are not limited to containing only iron. There are numerous other metallic minerals that can be extracted profitably from rocks.

When it contains fluorite or sulfur minerals in sufficient amounts to be extracted profitably: This statement is correct. Fluorite and sulfur are examples of non-metallic minerals that can be extracted profitably from rocks, and if a rock contains these minerals in sufficient quantities, it can be considered an ore.

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Answer:

The Inner Core

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Answer: b

explanation: i had the question on a test and got it right.

Answer:

677

Explanation:

took the test

it said that it was wrong but then it also said the total bond energy of the reactants is 677 kJ/mol. the correct one was 854, i guess.

Hydrogen and chlorine gases react to produce hydrochloric acid according to the reaction. 677 kJ/mol total bond energy  is in the products of the reaction. Therefore, option A is correct.

Bond strength in a chemical bond is measured by bond energy, often known as mean bond enthalpy or average bond enthalpy. According to IUPAC, bond energy is the average bond-dissociation energy in the gas phase for all bonds of the same type within a single chemical species.

In a chemical reaction, links between molecules are destroyed, and new bonds are created to create new molecules. For instance, hydrogen and oxygen are created when the bonds between two molecules of water are broken.

The quantity of bonds between atoms affects bond energy. A double bond, which consists of a single bond and an additional bond, is stronger than a single bond despite the fact that they are both weaker than each other.

Thus, 677 kJ/mol total bond energy, so option A is correct.

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The reactivity of elements generally increases as you go down a group in the periodic table. This is because elements in the same group have the same number of valence electrons, and as you go down a group, the number of valence electrons increases. This causes the atoms to have a higher positive charge, which makes them more reactive because they are more likely to form chemical bonds with other atoms.

However, the reactivity of elements decreases as you go down group 7 (the halogens) in the periodic table. This is because the valence shell of these elements is already full, so they are less likely to form chemical bonds with other atoms. As a result, the atoms in group 7 are less reactive than those in other groups.

₀n¹ -----------> ₁H¹ + ₋₁e⁰ + ν + q, Beta decay converts a neutron to a proton and emits an excessive-energy electron, producing a daughter nucleus with an equal mass.

Number as the parent and an atomic number that is higher by means of 1. Positron emission is the alternative to beta decay and converts a proton to a neutron plus a positron.

Two numbers are connected to the image. The variety on the upper right is the mass range, also referred to as the 'A' range. The 'A' wide variety describes the atomic weight of the atom and identifies the number of protons and neutrons within the nucleus.

In positron emission, additionally referred to as high-quality beta decay β+-decay, a proton within the determined nucleus decays right into a neutron that remains in the daughter nucleus, and the nucleus emits a neutrino and a positron, which is an advantageous particle like a regular electron in mass but of opposite price.

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Answer:

ver explicacion

Explanation:

Zn (s) + 2HCl (ac) ---> ZnCl2 (ac) + H2 (g)

El zinc se oxida y el hidrógeno se reduce. HCl es el agente oxidante mientras que Zn es el agente reductor.

2Na (s) + H2SO4 (ac) ----> Na2SO4 (ac) + H2 (g)

El Na se oxida y el hidrógeno se reduce. El ácido sulfúrico es el agente oxidante, mientras que el sodio metálico es el agente reductor de tge.

Ca (OH) 2 (ac) + H2CO3 (ac) ------> CaCO3 (s) + 2H2O (l)

Esta no es una reacción redox ya que no hay cambios en el número de oxidación de izquierda a derecha.

Answer:

b

Explanation:

Deuterium is the products of a hydrogen fusion reaction, the correct option is A.

It is the situation in which two hydrogen atoms merge or coalesce to form a helium atom.

A portion of the hydrogen's mass is transformed into energy during the process.

The fusion reaction that abilities the Sun and stars occurs when hydrogen atoms merge to produce deuterium, and then deuterium and hydrogen atoms fuse to form helium, releasing energy.

Four Hydrogen nuclei (protons) combine to form a Helium nucleus in the basic Hydrogen fusion cycle.  

Actually, electrons, neutrinos, and photons are involved in the hydrogen fusion into helium.

Since the total mass of the eventually results single nucleus is lower than the mass of the original two nuclei, the process releases energy.

Thus, the correct option for the given case is A.

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The amount of Br2 formed during the first 15.0 s of the reaction is 0.00300 moles.

To answer this question, we need to use the given rate law equation: rate = k[Br-][BrO3-]. We also know that the reaction is second order with respect to Br- and first order with respect to BrO3-.

In part b, we are given that the initial concentrations of Br- and BrO3- are both 0.0200 M. Therefore, the initial rate of the reaction can be calculated using the rate law equation:

initial rate = k[Br-][BrO3-] = k(0.0200 M)(0.0200 M) = 4.00 x 10^-6 M/s

Next, we can use the integrated rate law equation for a second-order reaction to calculate the amount of Br2 formed in the first 15.0 s:

1/[Br-]t - 1/[Br-]0 = kt
where [Br-]t is the concentration of Br- at time t, [Br-]0 is the initial concentration of Br-, and k is the rate constant.
Solving for [Br-]t, we get:

[Br-]t = 1/[kt + 1/[Br-]0]

Plugging in the values, we get:

[Br-]t = 1/[(4.00 x 10^-6 M/s)(15.0 s) + 1/0.0200 M] = 0.0186 M

Since the reaction is 1:1 stoichiometrically between Br- and BrO3-, the amount of Br2 formed in the first 15.0 s is equal to the amount of Br- consumed:

moles of Br2 = (0.0200 M - 0.0186 M)(1.50 L) = 0.00300 mol

Therefore, the amount of Br2 formed during the first 15.0 s of the reaction is 0.00300 moles.

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The solid does not react with a small amount of 3 M HNO3 is (D) silver chloride.

Your answer: (D) silver chloride does not react with a small amount of 3 M HNO3. This is because silver chloride is relatively insoluble in nitric acid, unlike the other solids which will react to form various products.

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The solid that does not react with a small amount of 3 M HNO₃ is silver chloride (AgCl). The correct option is (D).

Silver chloride is an insoluble ionic compound, which means it does not dissolve well in water or other common solvents. When HNO₃ (nitric acid) comes into contact with the other solids, chemical reactions occur.

(A) Calcium carbonate (CaCO₃) reacts with HNO₃, producing calcium nitrate (Ca(NO₃)₂), carbon dioxide (CO₂), and water (H₂O). This reaction is due to the acidic nature of HNO₃, which can cause the release of CO₂ from CaCO₃.

(B) Manganese(II) sulfide (MnS) reacts with HNO₃, producing manganese(II) nitrate (Mn(NO₃)₂), hydrogen sulfide (H₂S), and water (H₂O). In this case, the acid reacts with the sulfide, forming hydrogen sulfide gas as a product.

(C) Potassium sulfite (K₂SO₃) also reacts with HNO₃, resulting in the formation of potassium nitrate (KNO₃) and sulfuric acid (H₂SO₄). The acid reacts with the sulfite, creating a sulfate compound and a nitrate salt.

In conclusion, silver chloride (D) does not react with a small amount of 3 M HNO₃, while the other solids undergo chemical reactions when exposed to the acid. This is due to AgCl's insoluble nature and its inability to form new compounds under these conditions.

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Halogens are rarely found in native state because halogens are highly reactive.  

The group 17 elements are known as Halogen group. These elements include Fluorine, Chlorine, Bromine, Iodine and Astatine. Halogens react with metals to form salts. Halogens are non metals. Halogens are highly reactive and halogens are never found in pure form. Halogens not occur in free state.

Halogens have seven valence electrons in the outermost shell. The electronic configuration of Halogen is ns² np⁵.

Thus from the above conclusion we can say that Halogens are rarely found in native state because halogens are highly reactive.

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Calculate the mass, in amu, of 278 atoms of Li.

1) We need to find Li (Lithium) in the periodic table.

1) The atomic mass of Lithium is 6.94 u.

2) We can cancel some units and rearrange the equation.

3) Multiply the equation above by the number of atoms

The mass of 278 atoms of Lithium is 3.20*10^-21 u

First, we define density as:

Density = mass/volume;

We focus first on the volume of air in the room.

Volume:

We have the measurements of where the air is.

We calculate the volume with these measurements, but first, we change the units to L:

1 inch = 2.54 cm

1 L = 10^3 cm^3

1 ft = 12 inch

Now,

11.0 ft x (12 in/1 ft) x (2.54 cm/1 in) = 335.28 cm

12.0 ft = 365.76 cm

10.0 ft = 304.8 cm

Therefore, the volume of the room = 335.28 cm x 365.76 cm x 304.8 cm

Volume = 37378237.5 cm^3 x (1 L/10^3cm^3) = 374 x 10^2 L

From the Density equation, we clear the mass:

Density x volume = mass (g)

1.19 g/L x 374x10^2 L = 445x10^2 g x (1 kg/1000 g) = 44.5 kg

Answer: 44.5 kg

D. These are all traits of naturally occurring salt deposits.

Natural salt deposits form when bodies of water evaporate, leaving behind a layer of salt. These deposits can be found in many areas, often in layers of sedimentary rock. These deposits can also be very soluble in water, allowing them to flow and form domes or other structures.The natural deposits of salt (NaCl) are formed by the evaporation of salt- water, often in areas where  of water have become separated from the sea and have no outlet. These deposits are usually found in landlocked basins, such as deserts, salt flats, and salt domes .

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Answer:

Francium (Fr)

Explanation:

Looking at the periodic table, Francium has 7 energy levels as it is in the 7th Period and is in the 1st Group (meaning it has one electron in the outermost shell) which suggests that it has one valence electron.

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The statement that correctly identifies the type of mixture is that homogeneous mixtures have parts that are distributed evenly. The correct option is c.

A homogeneous mixture is sole in which the composition is consistent throughout the solution.

Since the dissolved salt is evenly distributed throughout the salt water sample, the salt water described as an illustration is homogeneous.

The statement that accurately defines the type of mixture is that homogeneous mixtures have evenly distributed parts.

Thus, the correct option is c.

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Answer:

Presence of an Electrolyte

Metal Surface

Oxygen or Other Oxidizing Agent

Difference in Potential

Electrochemical Pathway

Explanation:

We use Big O notation to describe the upper bound of a function in terms of its input size.

The order of inserting an element into a sorted list of size N implemented using array is O(N).

What is the order of inserting an element into a sorted list of size N implemented using array?

The order of inserting an element into a sorted list of size N implemented using array is O(N).

What is the formula for calculating Big O notation?

The Big O notation formula is O(g(n)) where g(n) is the rate of growth of the function in the equation.

In other words, we use Big O notation to describe the upper bound of a function in terms of its input size.

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The correct option is (B) AH° > 0 and AS° < 0.

The student can conclude that the enthalpy change (ΔH°) is positive (AH° > 0) and the entropy change (ΔS°) is negative (AS° < 0) for the reaction.

The equilibrium constant (K) is related to the standard Gibbs free energy change (ΔG°) by the equation:

ΔG° = -RTln(K)

At temperatures below 500 K, if the equilibrium constant (K) is greater than 1, it means that the standard Gibbs free energy change (ΔG°) is negative, indicating a spontaneous reaction.

1Since the standard Gibbs free energy change is given by the equation:

ΔG° = ΔH° - TΔS°

For the reaction to be spontaneous at temperatures below 500 K (ΔG° < 0), the term -TΔS° must dominate over ΔH°.

This implies that ΔH° must be positive (AH° > 0) and ΔS° must be negative (AS° < 0) to make the overall ΔG° negative and the reaction spontaneous.

On the other hand, at temperatures above 500 K, if the equilibrium constant (K) is less than 1, it means that the standard Gibbs free energy change (ΔG°) is positive, indicating a non-spontaneous reaction.

In this case, ΔH° must be negative (AH° < 0) and ΔS° must be positive (AS° > 0) to make the overall ΔG° positive and the reaction non-spontaneous.

Therefore, based on the information provided, the student can conclude that the values of AH° and AS° for the reaction are AH° > 0 and AS° < 0.

The correct option is (B) AH° > 0 and AS° < 0.

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Answer:

Answer

Change in temperature

It is an example of an endothermic reaction. It is absorbing heat.

Answer:

4.70 grams of NH4Cl is needed to prepare 350 mL of a 0.25 M ammonium chloride solution.

We need approximately 4.68 grams of NH4Cl to prepare a 0.25 M ammonium chloride solution with a volume of 350 mL.

To determine the mass of NH4Cl needed to prepare the solution, we us use the formula:

m=M x V x MM ... (i)

where,

m= mass in grams

M=molarity of solution

MM= molar mass of compound

V= volume in litres

The number of moles of NH4Cl needed can be calculated using:

  Moles = Molarity x Volume ...(ii)

  Moles = 0.25 mol/L x 0.350 L

  Moles = 0.0875 mol

Hence we can replace M x V with number of moles in equation i.

The molar mass of NH4Cl is :

  Molar mass of NH4Cl = (1 x 14.01 g/mol) + (4 x 1.01 g/mol) + (1 x 35.45 g/mol)

  Molar mass of NH4Cl = 53.49 g/mol

We have all the variables

Putting them in equation i.

Hence,

  Mass (g) = Moles x Molar mass

  Mass (g) = 0.0875 mol x 53.49 g/mol

  Mass (g) = 4.68 g

Therefore, you would need approximately 4.68 grams of NH4Cl to prepare a 0.25 M ammonium chloride solution with a volume of 350 mL.

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Answer:

n (moles) = m (mass) / M (molar mass)

Explanation:

divide the mass by the molar mass, and you have your answer

Hope you could understand.

If you have any query, feel free to ask.

Answer:

an oxygen atom with 8 electrons, 8 protons, and 9 neutrons

Explanation:

A proton has a positive charge and an electron has a negative charge. Magnitude of both of these charges is same. So, we need the same number of electrons and protons to make the atom neutral.

Neutron is neutral, so we can safely ignore it in this question.

Answer:

an oxygen atom with 8 electrons, 8 protons, and 9 neutrons

Explanation:

Answer:

26.00 units of Volume.....

The rate of change of the concentration of Na₂C₂O4 is -0.0551 M/s.

To determine the rate of change of the concentration of sodium oxalate (Na₂C₂O4), we can use the rate equation:

Rate = (Δ[Na₂C₂O4]) / (Δt)

where Δ[Na₂C₂O4] represents the change in concentration of Na₂C₂O4 and Δt represents the change in time.

In this case, the initial concentration of Na₂C₂O4 is 1.34 M, and after 19.3 seconds, the concentration is 0.276 M.

Substituting the values into the rate equation, we have:

Rate = (0.276 M - 1.34 M) / (19.3 s - 0 s)

Rate = (-1.064 M) / (19.3 s)

Rate = -0.0551 M/s

Therefore, the rate of change of the concentration of Na₂C₂O4 is -0.0551 M/s.

The negative sign indicates that the concentration of Na₂C₂O4 is decreasing over time, as the reactant is being consumed in the reaction.

It's important to note that the rate of a reaction is influenced by various factors, such as the reaction mechanism, temperature, and presence of catalysts. The rate can be determined experimentally by measuring the change in concentration of a reactant or product over a specific time interval.

The given information allows us to calculate the rate of change for the specific reaction involving Na₂C₂O4. However, without additional information about the reaction, it is not possible to determine the exact nature or stoichiometry of the reaction, as well as any other reactants or products involved.

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