how do you determine number of valence electrons an element has

Answer:

1455360 liters

Explanation:

If there are 3.79 liters in 1 gallon

Do 384,000 × 3.79

Which is 1455360

Answer:

Explanation:

C. 2p

The mass of the excess reagent remaining after completion of reaction, given that 8 g of magnesium is heated with 8 g of phosphorous is 0.98 g

First, we shall obtain the mass of the excess reagent that reacted. This is shown below:

6Mg + P₄ -> 2Mg₃P₂

From the balanced equation above,

145.8 g of Mg reacted with 124 g of P₄

Therefore,

8 g of Mg will react with = (8 × 124) / 145.8 = 7.02 g of P₄

Finally, we shall obtain the mass of the excess reagent remaining after the reaction. Details below:

Mass of excess reagent, P₄ remaining = Mass given - mass reacted

= 8 - 7.02

= 0.98 g

Thus, the mass of the excess reagent remaining after the reaction is 0.98 g

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Answer::

Explanation::

3.011  × 10²³ molecules are in 0.5 moles of PCl₃.

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,

Moles of PCl₃ = 0.5 moles

We know that 1 mole = 6.023 × 10²³ molecules

Thus, 0.5 moles will have 6.023 × 10²³ × 0.5 molecules.

= 3.011  × 10²³ molecules

Therefore, 3.011  × 10²³ molecules are in 0.5 moles of PCl₃.

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Answer: 0.79 atm

Explanation:

The Ideal Gas Law is PV=nRT.

since both Ar and O2 have the same volume and temperature, the only variable causing the differnce in pressure betwwen the 2 gases is the number of moles

the total pressure = the partial pressure of Ar + the partial  pressure of O2

1.024 atm = 0.447 amt + ?

so  

the total pressure of the bottle is 1.024 atm, what is the partial

pressure of O2 in the bottle? is PV

According to the information, we can infer that a 19.2-pound child would need to take approximately 2.49 tablets of 250.0 mg ampicillin per day.

To calculate the number of tablets the child needs to take, we first need to convert the weight of the child from pounds to kilograms. Since there are 2.20 pounds in 1 kg, we divide 19.2 pounds by 2.20 to get the weight in kilograms, which is approximately 8.73 kg.

Next, we calculate the daily dose of ampicillin for the child by multiplying the weight in kilograms by the recommended dosage of 115 mg/kg.

Since the available tablet size is 250.0 mg, we divide the total daily dose by the tablet size to find out how many tablets the child needs to take per day.

According to the above, we can infer that since we can't have a fraction of a tablet, we round the result to the nearest whole number. Therefore, a 19.2-pound child would need to take approximately 2.49 tablets (rounded to 2) of 250.0 mg ampicillin per day.

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Answer: potential energy

Explanation:  During a phase change, the heat added (PE increases) or released (PE decreases) will allow the molecules to move apart or come together. Heat absorbed causes the molecules to move farther apart by overcoming the intermolecular forces of attraction.

Answer:

\( \huge{ \boxed{111.30 \: \: \text{moles}}}\)

Explanation:

To find the number of moles in a substance given it's number of entities we use the formula

\( \bold{n = \frac{N}{L} \\ }\)

where

n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities.

From the question.

N = 6.7 × 10²⁵ \( \: H_2SO_4 \: \) molecules

\(n = \frac{6.7 \times {10}^{25} }{6.02 \times {10}^{23} } \\ = 111.2956...\)

We have the final answer as.

Answer:

the empirical formula is N2O

Answer:

1.76 * 6.02*10^23 = 1.05952*10^24

1.05952*2 = 2.11904 *10^24 oxygen and 1.05952*10^24 sulfur atoms

In 1.76 moles of SO₂, there are approximately 1.06 x 10²⁴ SO₂ molecules, 1.06 x 10²⁴ sulfur atoms, and 2.12 x 10²⁴ oxygen atoms. For determining the number of SO₂ molecules, sulfur atoms, and oxygen atoms in 1.76 moles of SO₂, we need to use Avogadro's number, which is approximately 6.022 x 10²³ particles per mole.

1 mole of any substance contains Avogadro's number of particles, which includes atoms or molecules. Therefore, to find the number of SO₂ molecules in 1.76 moles, we can multiply 1.76 moles by Avogadro's number:

Number of SO₂ molecules = 1.76 moles × Avogadro's number

Number of SO₂ molecules = 1.76 moles × 6.022 x 10²³ molecules/mol

Number of SO₂ molecules ≈ 1.06 x 10²⁴ molecules

Next, we can find the number of sulfur atoms and oxygen atoms in 1.76 moles of SO₂. In one molecule of SO₂, there is 1 sulfur atom and 2 oxygen atoms. So, the total number of sulfur atoms and oxygen atoms can be calculated as follows:

Number of sulfur atoms = Number of SO₂ molecules × 1 sulfur atom/molecule

Number of sulfur atoms = 1.06 x 10²⁴ molecules × 1 sulfur atom/molecule

Number of sulfur atoms ≈ 1.06 x 10²⁴ sulfur atoms

Number of oxygen atoms = Number of SO₂ molecules × 2 oxygen atoms/molecule

Number of oxygen atoms = 1.06 x 10²⁴ molecules × 2 oxygen atoms/molecule

Number of oxygen atoms ≈ 2.12 x 10²⁴ oxygen atoms

So, in 1.76 moles of SO₂, there are approximately 1.06 x 10²⁴ SO₂ molecules, 1.06 x 10²⁴ sulfur atoms, and 2.12 x 10²⁴ oxygen atoms.

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Answer:

Haematology is the specialty important for the diagnosis and management of a wide range of benign and malignant disorders of the red and white blood cells, platelets and the coagulation system in adults and children.

Answer:

The total pressure of a mixture of gases can be defined as the sum of the pressures of each individual gas: Ptotal=P1+P2+… +Pn. + P n . The partial pressure of an individual gas is equal to the total pressure multiplied by the mole fraction of that gas.

The new volume of a sample of gas that initially has a pressure of 3.2 atm and a volume of 345 ml is 120mL.

How to calculate volume?

The volume of a sample of gas can be calculated using the following formula:

P1V1 = P2V2

Where;

P1 = initial pressure

P2 = final pressure

V1 = initial volume

V2 = final volume

3.2 × 345 = 9.2 × V2

1104 = 9.2V2

V2 = 1104/9.2

V2 = 120

Therefore, the new volume of a sample of gas that initially has a pressure of 3.2 atm and a volume of 345 ml is 120mL.

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percentage yield =(actual yield/theoretical yield) ×100/1

chlorine is the limiting reagent hence would be the major determinant of the product

71[Cl2]=2×58.5[NaCl]

200[Cl2]=x[NaCl]

x=(200×58.5×2)/(71)

x=329.58g(theoretical yield of NaCl)

percentage yield = (240/329.58) ×100

percentage yield= 72.8℅

The answer is that the percentage yield is 72.8 % .

Chemical reactions in the real world do not always go exactly as planned on paper.

In the course of an experiment, many things will contribute to the formation of less product than would be predicted.

Besides spills and other experimental errors, there are often losses due to an incomplete reaction, undesirable side reactions, etc.

Chemists need a measurement that indicates how successful a reaction has been. This measurement is called the percent yield.

Percentage yield =(actual yield/theoretical yield) ×100 %

Chlorine is the limiting reagent hence would be the major determinant of the product

Molecular weight of Cl₂ is 71

Molecular weight of NaCl is 58.5

For 1 mole of Cl₂ 2 moles of NaCl is produced

so it is given that Cl₂ is 200 grams

= 200/71

=2.82 moles.

=5.63 moles of NaCl

=5.63* 58.5 grams

=329.58 g of Nacl

So , 329.58g is theoretical yield of NaCl

percentage yield = (240/329.58) ×100

percentage yield= 72.8℅

Therefore the percentage yield = 72.8%

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Answer:

d

Explanation:

higher no of particles are in CaCl2 solution

The depression in freezing point, elevation in boiling point, etc. are known as colligative particles. Here the CaCl2 solution has the higher boiling point and the NaCl solution has the lower freezing point. The correct option is D.

The properties of a dilute solution which depend only on the number of solute particles present in a given amount of solvent, and not in any way upon the nature of the solute particles are called colligative properties.

The elevation in boiling point is:

ΔTb = i × Kb × m

Here 'i' is the Van't Hoff factor, Kb is constant and 'm' is the molality.

The boiling point depends on the number of ions present in the electrolyte and the concentration. The number of ions in CaCl₂ is 3 whereas the number of ions in NaCl is 2.

ΔTb of CaCl₂ = 3 × 0.25 = 0.75

ΔTb of NaCl = 2 × 0.25 = 0.5

Similarly the freezing point depends on the number of particles of the electrolyte.

So CaCl₂ has boiling point and NaCl has low freezing point.

Thus the correct option is D.

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Answer:

A molecule made of two or more elements chemically combined is a compound.

A molecule made of two atoms of the same element is just that an element.

A molecule made of two ( or more) elements is a compound.

Explanation:

At equilibrium, the number of moles of \(Cl_2\) (g) will be 0.2025 mol.

1: Write the balanced chemical equation:

\(C_O\)(g) + \(Cl_2\)(g) ⟶ \(C_OCl_2\)(g)

2: Set up an ICE table to track the changes in moles of the substances involved in the reaction.

Initial:

\(C_O\)(g) = 0.3500 mol

\(Cl_2\)(g) = 0.05500 mol

\(C_OCl_2\)(g) = 0 mol

Change:

\(C_O\)(g) = -x

\(Cl_2\)(g) = -x

\(C_OCl_2\)(g) = +x

Equilibrium:

\(C_O\)(g) = 0.3500 - x mol

\(Cl_2\)(g) = 0.05500 - x mol

\(C_OCl_2\)(g) = x mol

3: Write the expression for the equilibrium constant (Kc) using the concentrations of the species involved:

Kc = [\(C_OCl_2\)(g)] / [\(C_O\)(g)] * [\(Cl_2\)(g)]

4: Substitute the given equilibrium constant (Kc) value into the expression:

1.2 x \(10^3\) = x / (0.3500 - x) * (0.05500 - x)

5: Solve the equation for x. Rearrange the equation to obtain a quadratic equation:

1.2 x \(10^3\) * (0.3500 - x) * (0.05500 - x) = x

6: Simplify and solve the quadratic equation. This can be done by multiplying out the terms, rearranging the equation to standard quadratic form, and then using the quadratic formula.

7: After solving the quadratic equation, you will find two possible values for x. However, since the number of moles cannot be negative, we discard the negative solution.

8: The positive value of x represents the number of moles of \(Cl_2\)(g) at equilibrium. Substitute the value of x into the expression for \(Cl_2\)(g):

\(Cl_2\)(g) = 0.05500 - x

9: Calculate the value of \(Cl_2\)(g) at equilibrium:

\(Cl_2\)(g) = 0.05500 - x

\(Cl_2\)(g) = 0.05500 - (positive value of x)

10: Calculate the final value of \(Cl_2\) (g) at equilibrium to get the answer.

Therefore, at equilibrium, the number of moles of \(Cl_2\) (g) will be 0.2025 mol.

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Taking into account the reaction stoichiometry, 1 mole of H₂ can be produced by reacting 2 moles of HCI.

In first place, the balanced reaction is:

Mg + 2 HCl  → MgCl₂ + H₂

By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:

By reaction stoichiometry 2 moles of HCl form 1 mole of H₂.

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Reverse the sign of the second equation, change the sign of the enthalpy and add. Option B

The enthalpy could be obtained by the use of the Hess law of constant heat summation. As such, we have a number steps and it is possible for use to obtain the enthalpy of the final reaction as shown by a series of manipulations.

By inspection, we can see that, if we desire to obtain the enthalpy of the final reaction as shown, then we have to reverse the sign of the second equation, change the sign of the enthalpy and add. Option B

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Answer:

neutralization reaction is when an acid and a base react to form water and salt and involves the combination of hydrogen ions and hydroxyl ions to generate water. The neutralization of a strong acid and strong base has a pH equal to 7.

Answer:

Ca

Explanation:

It is on the left side of the periodic table where metals are located.

Answer:

Ca

Explanation:

Answer: three

Explanation:

Answer:

1. lakes and rivers 2. groundwater 3. watershed 4. pollution

Explanation:

Answer:

SiO2

Explanation:

Si + O2 → SiO2

A pH of 4 is ten times more acidic than a pH of 5.

Yes, pH can have decimal values. In fact, pH values can range from 0 to 14 and can have any value between them including decimals. pH is a measure of the acidity or alkalinity of a solution, and it is determined by the concentration of hydrogen ions (H+) in the solution.A solution with a pH of 7 is neutral, which means that it has an equal concentration of hydrogen ions (H+) and hydroxide ions (OH-). An acidic solution has a pH below 7 and a high concentration of H+ ions. On the other hand, an alkaline solution has a pH above 7 and a low concentration of H+ ions.A pH that is less than 7.0 indicates acidity. pH less than 7.0 is acidic while pH greater than 7.0 is alkaline. Each number on the pH scale represents a ten-fold change in the acidity/alkalinity of the solution. For example, a pH of 5 is 10 times more acidic than a pH of 6, and 100 times more acidic than a pH of 7.A pH of 0 indicates a very strong acidic solution while a pH of 14 indicates a very strong alkaline solution. It's worth noting that pH is a logarithmic scale, meaning that a change of one pH unit corresponds to a ten-fold change in hydrogen ion concentration.

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The minimum entropy change of the heat-supplying source is -0.87 kJ/K.

In this case, given the initial conditions, we first use the 10-% quality to compute the initial entropy.

S₁ = 1.485  +  (0.1)(5.6865) = 2.0537 kJ/kg K

The entropy at the final state given the new 40-% quality:

S₂ = 1.4337  +  (0.4)(5.7894) = 3.7495 kJ/kg K

m₁ = 0.026/(0.001057   +  0.1 x 1.002643) = 0.257 kg

m₂ = 0.026/(0.001053   +  0.4 x 1.158347)  = 0.056 kg

ΔS + S₁  - S₂  + S₂m₂  - S₁m₁  -  sfg(m₂  -  m₁)  > 0

ΔS + 2.0537 -  3.7495 + (3.7495 x 0.056)  -   (2.0537 x 0.257)  - 5.6865( 0.056 - 0.257)  >  0

ΔS > -0.87 kJ/K

Thus, the minimum entropy change of the heat-supplying source is -0.87 kJ/K.

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