What is the correct answer please help

Answer:

a. Na2CO3 (s) + 2HCl (aq) → 2NaCl (aq) + H2O (l) + CO2 (g)

b. 2NaBr (aq) + Ca(OH)2 (aq)→ CaBr2 (aq) + 2NaOH (aq)

c. 2NH3 (g) + H2SO4 (aq)→ (NH4)2SO4 (aq)

d. 4C5H9O (l) + 27O2 (g)→ 20CO2 (g) + 18H2O (l)

Explanation:

a. Na2CO3 (s) + 2HCl (aq) → 2NaCl (aq) + H2O (l) + CO2 (g)

b. 2NaBr (aq) + Ca(OH)2 (aq)→ CaBr2 (aq) + 2NaOH (aq)

c. 2NH3 (g) + H2SO4 (aq)→ (NH4)2SO4 (aq)

d. 4C5H9O (l) + 27O2 (g)→ 20CO2 (g) + 18H2O (l)

Answer:

To determine the pressure change when a constant volume of gas is cooled from 40°C to 20°C, we can use the ideal gas law, which relates the pressure, volume, temperature, and number of moles of a gas:

PV = nRT

where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature in Kelvin.

Since we are dealing with a constant volume of gas, we can simplify the ideal gas law to:

P1/T1 = P2/T2

where P1 and T1 are the initial pressure and temperature, and P2 and T2 are the final pressure and temperature.

Converting the temperatures to Kelvin:

T1 = 40°C + 273.15 = 313.15 K

T2 = 20°C + 273.15 = 293.15 K

Substituting the values into the equation:

10 atm / 313.15 K = P2 / 293.15 K

Solving for P2:

P2 = (10 atm / 313.15 K) x 293.15 K

P2 = 9.354 atm

Therefore, the pressure of the gas decreases from 10 atm to 9.354 atm when cooled from 40°C to 20°C at constant volume.

In the following ions, the one which is soluble in water when paired with Ca²+, according to the solubility rules chart is Cl-.

What is solubility rules chart?

Solubility is applicable to many laboratory processes and is also important in medicine. Some ions can be toxic when they separate in a solution but are helpful as part of a compound.

Solubility rules chart is a chart that helps us to find which anion is soluble in water with which cation.

Given is the Ca²⁺ cation and according to the solubility rules chart, Chloride (Cl⁻) - soluble in water

Hydroxide (OH⁻) - very slightly soluble

Carbonate (CO3²⁻) - insoluble

Sulfate (SO4²⁻) - very slightly soluble

Therefore, in the following ions, the one which is soluble in water when paired with Ca²+, according to the solubility rules chart is Cl-.

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Answer:

Chloride (Cl-)

Explanation:

Explanation:

Refer to pic..........

There are 5 atοms οf gοld (Au) are in a US Eagle gοld bulliοn cοin with a mass οf 31.3g Au.

A substance's tiniest cοmpοnent that cannοt be destrοyed chemically. A prοtοn (a pοsitive particle) and a neutrοn (a neutral particle) make up the nucleus (center) οf each atοm (particles with nο charge). The nucleus is filled with negative electrοns. Chemical reactiοns cannοt generate οr destrοy atοms since they are indivisible particles.

The amοunt οf matter in a bοdy is referred tο as its mass. The kilοgrams is the kilοgrams, which is the SI unit οf mass (kg). Mass is defined as: Mass = Density /Vοlume.

Therefοre, There are 5 atοms οf gοld (Au) are in a US Eagle gοld bulliοn cοin with a mass οf 31.3g Au.

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The number of moles in 20g of Ne is 1 mole.

The mole is an amount unit similar to familiar units like pair, dozen, gross, etc. It provides a specific measure of the number of atoms or molecules in a bulk sample of matter.

A mole is defined as the amount of substance containing the same number of atoms, molecules, ions, etc. as the number of atoms in a sample of pure 12C weighing exactly 12 g.

Given,

Mass of Ne = 20g

Molar mass of Ne = 20 g/mole

Moles = mass ÷ molar mass

              = 20 ÷ 20

               = 1 mole

Therefore, the number of moles in 20g of Ne is 1 mole.

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The question has spelling mistake. Probably the question is:

Calculate the number of moles in 20g of neon.

Normal Concentration = 18.09 moles/L Standard Deviation = 1.89 moles/L

The capacity for sustained attention on a single thing, activity, or work without being sidetracked is known as concentration. It is the key to success in most endeavors, as it requires a person to ignore any extraneous thoughts, feelings, or stimuli and instead focus on the task at hand. Concentration is a mental skill that can be developed and improved with practice, such as with mindfulness, meditation, and various cognitive exercises. Concentration can also be adversely affected by poor physical health, lack of sleep, and stress, so it is important to maintain a healthy lifestyle if one wants to stay focused.
Student | Weight (g) | Volume (L) | Concentration (moles/L)
1 | 5.0 | 0.25 | 19.82
2 | 8.0 | 0.50 | 15.89
3 | 4.0 | 0.20 | 20.23
4 | 7.0 | 0.30 | 18.52
5 | 6.0 | 0.40 | 16.96

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the percent by mass of cashews and almonds can be determined by the Percentage by mass of X = (mass of X / total mass of mixed nuts) x 100%

A possible plan to determine the percentage by mass of cashews and almonds in a jar of mixed nuts could be:

Obtain a sample of the mixed nuts and weigh it to determine the total mass of the sample.

Separate the cashews and almonds from the rest of the nuts in the sample.

Weigh the separated cashews and record the mass.

Weigh the separated almonds and record the mass.

Calculate the percentage by mass of cashews and almonds in the mixed nuts by using the following formulas:

Percentage by mass of cashews = (mass of cashews / total mass of mixed nuts) x 100%

Percentage by mass of almonds = (mass of almonds / total mass of mixed nuts) x 100%

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The carburizing time necessary to achieve a carbon concentration of 0.30 wt% at a position 4 mm into an iron-carbon alloy is 63.4 hours.

To determine the carburizing time necessary to achieve a carbon concentration of 0.30 wt% at a position 4 mm into an iron-carbon alloy, we can use Fick's second law of diffusion:

[tex]DC_{surface} / 2 = (C_{surface} - C_{4mm}) / erf(x / (2 * \sqrt{Dt} ))\\[/tex]

where D is the diffusion coefficient, [tex]C{surface}\\[/tex] is the surface carbon concentration (0.90 wt%), C_4mm is the carbon concentration at the position 4 mm into the alloy (0.10 wt%), x is the distance from the surface (4 mm), and t is the carburizing time we want to find.

We can use the diffusion coefficient for γ-Fe at 1100°C from Table 5.2, which is D = [tex]6.0 * 10^{-12} m^2/s.[/tex]

Substituting the given values, we get:

[tex](6.0 * 10^{-12} m^2/s) * (0.90 - 0.30) / 2 = (0.90 - 0.10) / erf(4 mm / (2 * \sqrt{6.0 * 10^{-12} m^2/s} ))[/tex]

Simplifying the left-hand side, we get:

[tex]1.8 * 10^{-12} m^2/s = (0.80) / erf(4 mm / (2 * \sqrt{(6.0 * 10^{-12} m^2/s) * t)})))[/tex]

Taking the inverse error function of both sides, we get:

[tex]erf(4 mm / (2 * \sqrt{6.0 * 10^{-12} m^2/s) * t)} ) = 0.000346[/tex]

Substituting this back into the previous equation, we get:

[tex]1.8 * 10^{-12} m^2/s = (0.80) / 0.000346[/tex]

Solving for t, we get:

t = 63.4 hours

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According to the gravitational force, your  mass would stay the same but you would weigh less.

Force is defined as a cause which is capable of changing the motion of an object. It can cause an object which has mass to change it's velocity. It is also simply a push or a pull . It has both magnitude as well as direction.Hence, it is a vector quantity.

It has SI units of Newton and is represented by'F'.Newton's second law states that force which acts on an object is equal to momentum which changes with time. If mass of object is constant, acceleration is directly proportional to net force acting on an object.

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The pH after the following volumes of titrant have been added 0 ml 20 mL 59. 1 mL 60. 0 mL 71. 4 mL 73. 4 mL are 11.89, 11.89, 8.45, 8.45, 7.98, 8.95 respectively.

The reaction between NH3 and HCl can be represented by the following equation: NH3 + HCl → NH4+ + Cl-

To calculate the pH after different volumes of titrant have been added, we need to determine the amount of titrant that has reacted with the analyte and the resulting concentration of the products.

A. 0 mL of titrant (initial state)

At the start, there is no titrant added to the analyte, so the concentration of NH3 is 0.050 M. NH3 is a weak base, so we can use the Kb expression to calculate the concentration of OH-:

[tex]Kb = [NH4+][OH-] / [NH3][/tex]

[tex]1.8 * 10^{-5} = x^2 / (0.050 - x)[/tex]

initial concentration of NH3 is much greater than the initial concentration of HCl, we can assume that the concentration of NH3 does not change significantly during the titration.

[tex]Kb = x^2 / 0.050\\x = \sqrt{Kb * 0.050} = 1.3 * 10^{-3} M[/tex]

The concentration of OH- is equal to [tex]1.3 * 10^{-3} M[/tex], so we can calculate the pH:

[tex]pH = 14 - pOH = 14 - (-log[OH-]) = 11.89[/tex]

Therefore, the pH at the start of the titration is 11.89.

B. 20 mL of titrant

After adding 20 mL of 0.025 M HCl, the volume of the solution is 50 mL (30 mL NH3 + 20 mL HCl). The moles of HCl added is:

moles of HCl = volume x concentration = 0.020 L x 0.025 mol/L = 5 x 10^-4 mol

Since the reaction is a 1:1 reaction, the moles of NH3 remaining is equal to the moles of HCl added.

concentration of NH3 = moles of NH3 / volume of NH3 = (0.050 mol/L x 0.030 L - 5 x 10^-4 mol) / 0.030 L = 0.048 mol/L

Since the concentration of NH3 has decreased, we need to recalculate the concentration of OH- using the new concentration of NH3:

[tex]Kb = [NH4+][OH-] / [NH3]\\1.8 * 10^{-5} = x^2 / (0.048 - x)[/tex]

Solving for x, we get:

[tex]x = 1.3 * 10^{-3} M[/tex]

The concentration of OH- is still [tex]x = 1.3 * 10^{-3} M[/tex], so we can calculate the pH:

pH = 14 - pOH = 14 - (-log[OH-]) = 11.89

Therefore, the pH after adding 20 mL of titrant is still 11.89.

Similarly for  C. 59.1 mL of titrant

The pH after adding 59.1 mL of titrant is 8.45.

D. 60 mL of titrant

The pH after adding 60 mL of titrant is 8.45.

E. 71.4 mL of titrant

The pH after adding 71.4 mL of titrant is 7.98.

F. 73.4 mL of titrant

The pH after adding 73.4 mL of titrant is 8.95.

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35.5 grammes of sodium tetraoxosulphate (VI) were produced.

Solution: 0.5 m of NaOH denotes the amount of the solvent that is dissolved in 0.5 mole (20.0 g) of NaOH. 0.5 moles of NaOH (20.0 g) are dissolved in 1000 millilitres of the solution, or 0.5 M of NaOH.

Tetraoxosulphate VI acid is produced commercially using the Contact process. The Contact procedure entails the following steps. In order to purge the sulphur (IV) oxide generated of contaminants and dust that can poison the catalyst, it is combined with extra air and sent through an electric chamber.

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The concentration of K2CO3 (Potassium carbonate) in the solution is 0.000235 M.

To determine the concentration of K2CO3 in a solution, we need to calculate the number of moles of K2CO3 and divide it by the total volume of the solution.

First, let's calculate the number of moles of K2CO3:

molar mass of K2CO3 = 2(39.1 g/mol) + 12.0 g/mol + 3(16.0 g/mol) = 138.2 g/mol

moles of K2CO3 = 17.8 g / 138.2 g/mol = 0.1287 mol

Next, let's calculate the total volume of the solution:

total mass of solution = 546 g

Assuming the density of the solution is 1 g/mL, we can find the volume of the solution:

volume of solution = 546 mL

Finally, we can calculate the concentration of K2CO3:

concentration of K2CO3 = moles of K2CO3 / volume of solution

= 0.1287 mol / 546 mL

= 0.000235 M

Therefore, the concentration of K2CO3 in the solution is 0.000235 M.

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The evidence cards that support Claim 1 are the manufacturer's instructions which indicate that the POW kit is designed to heat water and the evidence cards that support Claim 2 are a separate study which found that the POW kits only heated the water to an average temperature of 50°C.

What is temperature?

Temperature is a measure of the degree of hotness or coldness of an object or substance. It is a physical quantity that describes the average kinetic energy of the particles in a system, where higher temperatures indicate that the particles are moving faster and have more energy, while lower temperatures indicate that the particles are moving slower and have less energy. Temperature is typically measured using a thermometer and is expressed in units such as Celsius (°C) or Fahrenheit (°F).

The evidence cards that support Claim 1 are:

The evidence cards that support Claim 2 are:

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Answer: 4129.38 kPa

Explanation:

P=nRT/V= 25 molesx 8.314 x 298.15 / 15=

Answer:

I think it is Al2O3

The electron that has returned to ground state is 5.

In the case of an atom, the ground state refers to the lowest possible energy level that an electron can occupy. This is the energy level closest to the nucleus and is often referred to as the "1s" orbital.

Electrons can occupy higher energy levels by absorbing energy and moving to an excited state, but they will naturally return to the ground state by releasing the excess energy in the form of electromagnetic radiation, such as light.

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Explanation:

To solve this problem, we can use the ideal gas law, which states:

PV = nRT

where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature.

At STP (standard temperature and pressure), the pressure is 1 atm and the temperature is 273 K (0°C). We can use these values to find the number of moles of propane gas in the can:

P1V1 = nRT1

n = P1V1 / (RT1)

= (0.500 atm) * (0.456 L) / (0.0821 Latm/(mol*K) * 296 K)

= 0.0103 mol

Next, we can use the molar volume of a gas at STP (22.4 L/mol) to find the volume that the propane would occupy at STP:

V2 = n * Vm

= 0.0103 mol * 22.4 L/mol

= 0.231 L

Therefore, the volume that the propane would occupy at STP is approximately 0.231 L (or 231 mL).

The compounds that would form precipitates are; CuCO3 and Ca(OH)2 and  ZnS

Some compounds form precipitates in aqueous solutions because their solubility decreases as the temperature or concentration of the solution changes. When the solubility limit of the compound is reached, the excess solid particles will no longer dissolve and will start to form a solid precipitate.

Precipitation reactions can be useful in analytical chemistry for detecting and identifying ions in solution. They can also be used in industrial processes, such as the purification of metals and the removal of impurities from wastewater.

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Answer:

D. 80 p+, 124 nº, 78 e-

Explanation:

The atomic number of mercury (Hg) is 80, which means it has 80 protons and 80 electrons in a neutral atom. The ion given is Hg2+ which means it has lost two electrons, so the number of electrons is now 80 - 2 = 78.

The mass number of mercury is 204, which means it has  204 nucleons in its nucleus. Since the ion is Hg2+, there are two mercury atoms present. Therefore, the total number of protons is 2 × 80 = 160, and the total number of neutrons is 204 - 160 = 44.

So the answer is D) 80 p+, 124 nº, 78 e-

There are different types of mixtures that we use everyday. The salt solution, sugar solution, the curry for food, salads etc. are all mixtures.

Mixtures are combination of two or more individual components mixed by physical adherence or through chemical bonding. There are two types of mixtures homogenous and heterogenous mixtures.

In homogenous mixtures, the components are forming a single phase and appear to be one substance. For example, sugar solution, salt solution etc. are homogenous mixtures.

Components in a heterogenous mixture are clearly distinguishable. They form different phases or layers in the mixture. Curry for food, salads, and many other food items are mixtures of different components.

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C. It must have a full or partial charge.

When a particle dissolves in water, it becomes surrounded by water molecules. The polarity of water molecules allows them to interact with other polar molecules, including ions or molecules that have a full or partial charge.

These interactions between the charged particle and water molecules help to break apart the intermolecular forces holding the particle together and allow it to dissolve in water.

Particles that lack a full or partial charge, such as those with nonpolar covalent bonds or areas of neutral charge, typically do not dissolve well in water.

These types of particles do not have a strong attraction to the polar water molecules and do not experience the same breaking of intermolecular forces that charged particles do.

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The type of energy being transferred to the pot to make the water boil is heat energy. The heat energy is transferred from the stove to the pot, which then transfers the heat energy to the water molecules.

Simply said, sound energy is a result of vibrations passing through a substance. Sound waves can travel through solids, liquids, and gases. When a force, such as sound or pressure, causes an item or substance to vibrate, the result is sound energy. Waves of that energy pass through the substance. We refer to the sound waves as kinetic mechanical energy.

The wind chime's rich, bright tones or its high, delicate tingling Traffic noises include the rumbling of engines, screeching tyres, loud radios, and squeaking brakes. infants' cries and babbling. As the water molecules absorb the heat energy, they begin to move faster and eventually reach a point where they turn into vapor, causing the water to boil.

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Answer: 10.06 g

Explanation:

PV = nRT,

substitute the values into the equation

At STP, pressure (P) is 1 atm and temperature (T) is 273 K. The value of R is 0.0821 L*atm/mol*K.

PV = nRT

(1 atm) (15.9 L) = n (0.0821 L•atm/mol•K) (273 K)

solve for n

n = (1 atm x 15.9 L) / (0.0821 L•atm/mol•K x 273 K)

n = 0.627 moles of methane

caluclate using its molar mass

mass = n * molar mass

mass = 0.627 mol x 16.04 g/mol

mass = 10.06 g

Answer: Highly Inflammable. Natural gas is a highly flammable substance that can cause significantly more damage should there be an accident. ...

Greenhouse Gas Emissions. ...

Non-Renewable. ...

Not Easy to Use. ...

Expensive Pipelines.

Explanation:

The mass of NaCl is 58.5 g

The mole is a fundamental unit of measurement used in chemistry to express the amount of a substance. One mole of a substance is defined as the amount of that substance that contains the same number of entities, such as atoms, molecules, or ions, as there are in 12 grams of carbon-12. This number is known as Avogadro's number and is approximately 6.02 x 10^23.

Number of moles of NaOH = 40 g/40 g/mol = 1 mole

Since the reaction is 1:1

Mass of NaCl formed = 1 moles * 58.5 g/mol = 58.5 g

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Eons are the current name for the large units of time that make up the geologic time scale. Eons can be further broken down into eras, which are then further broken down into periods.

The evolution of life on Earth is frequently depicted alongside the geologic time scale. It occasionally also refers to significant occurrences on Earth, such as the creation of the world's great mountains or the demise of the dinosaurs.

1. Since fossils revealed similar organisms coexisting on Earth at various periods of time, scientists divided Earth's history into several periods. To keep track of how Earth has changed, they gave each period of time a name.

For instance, the Jurassic period included a large number of dinosaurs. Fossils of the planet's very earliest green vegetation from the Ordovician period have been discovered. European scientists made up a large portion of those who originally gave historical periods on Earth names.

2. During the Precambrian age in earth, multicellular organisms are believed to be evolved. The development of life significantly started at the Precambrian era.

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If 6. 5 moles of nitrogen gas react with 17. 8 moles of hydrogen gas, mass of ammonia that would be produced is 34g.

In the reaction N2 + 3H2 → 2NH3, 6.5 moles of nitrogen gas and 17.8 moles of hydrogen gas will react to produce 2 moles of ammonia. To calculate the mass of ammonia produced, we can use the formula:

Mass = moles x molar mass

So, in this case, the mass of ammonia produced would be:

Mass = 2 moles x 17 g/mol = 34 g

The mass of one mole of a material, given in grams per mole (g/mol), is known as molar mass. It is computed by multiplying the atomic masses of all the atoms in a molecule or formula unit.

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By placing a thermometer throughout the reaction mixture to observe temperature changes, endothermic and exothermic reaction can be identified.

Both exothermic and endothermic reactions are chemical processes in which heat is absorbed and released. Photosynthesis is a nice example of such an endothermic process. An example of just an exothermic process is combustion.

The temperature of a reaction mixture rises as energy escapes in an exothermic process. The temperature drops as the energy is taken in in an endothermic process. Place a thermometer throughout the reaction mixture to observe temperature changes.

Therefore, by placing a thermometer throughout the reaction mixture to observe temperature changes, endothermic and exothermic reaction can be identified.

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The number of atoms in 0.0082g of gold is 2.50 x 10^19 atoms.

What is a molar mass in chemistry?

Molar mass is the mass of one mole of a substance, usually expressed in grams per mole (g/mol). It is a fundamental concept in chemistry that allows us to relate the mass of a substance to the number of atoms or molecules present.

The molar mass of gold (Au) is approximately 197 g/mol. To find the number of atoms in 0.0082 g of gold, we first need to calculate the number of moles of gold present:

moles of gold = mass of gold / molar mass of gold moles of gold = 0.0082 g / 197 g/mol moles of gold = 4.16 x 10^-5 mol

Next, we can use Avogadro's number (6.022 x 10^23 atoms/mol) to convert the number of moles to the number of atoms:

number of atoms = moles of gold x Avogadro's number number of atoms = 4.16 x 10^-5 mol x 6.022 x 10^23 atoms/mol number of atoms = 2.50 x 10^19 atoms

Therefore, there are approximately 2.50 x 10^19 atoms in 0.0082 g of gold.

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