If a solution of hf (ka = 6.8 10-4) has a ph of 3.67, calculate the total concentration of hydrofluoric acid.

number of moles of SCN⁻ = 0 .001 X 3 / 1000 = 3 X 10⁻⁶ moles    in the 25 ml of solution

2) SCN⁻ + Fe³⁺ ===> FeNCS²⁺

1 mole SCN⁻ produces 1 mole of FeNCS²⁺

Therefore moles of FeNCS²⁺ in 25 ml = 3 X 10⁻⁶

Molar Concentration of FeNCS²⁺ = (3 X10⁻⁶ )X 1000 / 25 = 1.2 X 10⁻⁴ Moles / liter

The molar concentration of Fe(SCN)²+ is 3.52 × 10⁻² M, assuming all SCN⁻ is complexed with Fe³+. Thus, the concentration of Fe(SCN)²+ is equal to 3.52 × 10⁻² M.

The molar concentration of Fe(SCN)²+, assume that all of the SCN⁻ is complexed with Fe³+ to form Fe(SCN)²+. The concentration of Fe(SCN)²+ after 10 s is 3.52 × 10⁻² M under conditions of excess Fe³+.

Therefore, the molar concentration of Fe(SCN)²+ is 3.52 × 10⁻² M. The reaction is stoichiometric, meaning the initial concentration of SCN⁻ is converted entirely to Fe(SCN)²+.

You need to add 4.043 grams of anhydrous calcium bromide (CaBr2) to make a 0.202 M aqueous solution in a 125 mL volumetric flask.

To calculate the mass of CaBr2 needed, use the formula molarity  imes volume (in liters)  imes molar mass. The molarity is given as 0.202 M, and the volume needs to be converted to liters (0.125 L). The molar mass of CaBr2 is approximately 199.9 g/mol. Multiplying these values gives us the mass in grams:

0.202 mol/L  imes 0.125 L  imes 199.9 g/mol = 5.0475 g

However, since mass must be measured accurately in the laboratory, this final result must be weighed correctly using a balance and all the necessary safety precautions must be observed when handling calcium bromide.

Answer:

4.245 × 10²¹ cubic centimetre of Fe

Explanation:

First step is to find the number of atoms that is present in Fe(Iron)

The atomic mass of Fe(iron) is  55.845

We  have to convert  the atomic weight into grams

1 atomic mass = 1.66 x 10⁻²⁴grams

55.845(atomic mass of Fe) =

55.845 x 1.66 x 10 ⁻²⁴ grams = 9.27 x 10²² grams.

Therefore, the number of atoms in a cubic centimetre of Fe (Iron) =

Density of Fe(solid) ÷ number of grams of Fe

Density of Fe (solid) is known as = 7.874g/cm³

The number of atoms in a cubic centimetre of Fe (Iron =

7.874g/cm³ ÷9.27 x 10²²grams

= 8.494 × 10²¹atoms.

In the question we are told Fe adopted a body centered cubic unit cell

Hence , in Body centered cubic unit cell, we have:

We have one atom at the 8 corners of a cube

We also have one body atom the cube's center

8 corners × 1/8 per corner atom = 8 × 1/8 = 1 atom

(8 corners × 1/8 per corner atom) + (1× 1) = 2 atoms

Therefore, the total number of featoms present per unit cell = 2 atoms.

The number of unit cells are present per cubic centimeter of Fe =

Number of Fe atoms per cubic centimeter ÷ Number of Fe per unit cell

= 8.494 × 10²¹ atoms ÷ 2 atoms.

= 4.247 × 10²¹ cubic centimetre of Fe

Hence the number of unit cells that are present per cubic centimeter of Fe is

4.247 × 10²¹ cubic centimetre of Fe.

[tex]\boxed{\text{Deposition}}[/tex] is shown in the given model.

Further Explanation:

Condensation

The process by which a substance in its gaseous or vapor form is transformed into its liquid form is termed as condensation. It is just the reverse of evaporation. The random motion of gas particles is reduced and they come together to form a liquid. This is done by altering the temperature and pressure of the substance.

Deposition

The phase transition due to which a gas or vapor transforms directly into solid by not going through the liquid phase is termed as deposition. It is a thermodynamic process. This process occurs when water vapors release enough of its thermal energy and get converted into solids directly without passing through the liquid state. It is the opposite of what is done in the sublimation process and is therefore known as desublimation.

Boiling

The phase transition due to which gaseous or vapor state is formed from the liquid state is known as boiling. This takes place when a substance in its liquid state is heated to its boiling point.

Freezing

It is a process in which the substance gets converted from its liquid state to a solid state. It is just the reverse of melting. In this phase transition, heat is released from the substance and the liquid particles come closer to form solid. The formation of ice is an example of freezing.

In the given model, gaseous or vapor state is transformed into a solid state and this phase change occurs in case of deposition. Therefore deposition is shown in the given model.

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Answer details:

Grade: Senior School

Chapter: Phase transition

Subject: Chemistry

Keywords: deposition, freezing, boiling, solid, liquid, vapor, condensation, desublimation, thermodynamic process.

The quantum numbers (4, 2, 1, +½) and (4, 1, 1, +½) represent two different electrons in an atom.

The first quantum number, n, represents the principal energy level, which is 4 for both electrons.

The second quantum number, l, refers to the type of subshell, where l = 2 corresponds to the d subshell and l = 1 corresponds to the p subshell.

The third quantum number, m₁, specifies the specific orbital within the subshell. For the electron (4, 2, 1, +½), m₁ = 1, indicating a specific orbital within the d subshell. For the electron (4, 1, 1, +½), m₁ = 1, indicating a specific orbital within the p subshell.

The fourth quantum number, m², represents the spin of the electron. In both cases, it is +½, indicating a spin up orientation for both electrons.

The quantum numbers (4, 2, 1, +½) and (4, 1, 1, +½) represent two different electrons in an atom. The first quantum number, n, represents the principal energy level, which is 4 for both electrons. The second quantum number, l, refers to the type of subshell, where l = 2 corresponds to the d subshell and l = 1 corresponds to the p subshell.

The third quantum number, m₁, specifies the specific orbital within the subshell. For the electron (4, 2, 1, +½), m₁ = 1, indicating a specific orbital within the d subshell. For the electron (4, 1, 1, +½), m₁ = 1, indicating a specific orbital within the p subshell.

The fourth quantum number, m², represents the spin of the electron. In both cases, it is +½, indicating a spin up orientation for both electrons.

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Answer: The pressure under the water is 7.29 atm

Explanation:

We are given:

Pressure under the water = 739 kPa

To convert into atm, we use the conversion factor:

1 atm = 101.325 kPa

Converting the pressure from kilo pascals to atmospheres, we get:

[tex]\Rightarrow 739kPa\times \frac{1atm}{101.325kPa}=7.29atm[/tex]

Hence, the pressure under the water is 7.29 atm

Answer:

Solar radiation

Explanation:

In general there are three forms of energy: heat, light and sound. Energy transfer takes place as energy moves from one object to another in a certain medium or in vacuum.

The heat energy or the electromagnetic energy from sun strikes the earth surface in the form of radiation. This is also called solar energy or solar radiation.

The energy required to heat the silver cube from 15°C to 32°C can be calculated via the formula for heat transfer. The mass of the silver cube is calculated to be 210g using the given volume and density.

The energy required to heat a substance is calculated using the formula q = mcΔT, where 'q' is the heat energy, 'm' is the mass, 'c' is the specific heat capacity and 'ΔT' is the change in temperature.

The volume of the silver cube is given as 20.0 cm3. The density of silver is given as 10.5 g/cm3. Therefore, you can calculate the mass of the silver cube by multiplying the volume with the density, that is m = volume x density = 20.0 cm3 x 10.5 g/cm3 = 210 g.

The specific heat capacity for silver, c, is given to be 0.235 J/g°C. The change in temperature, ΔT, is final temperature - initial temperature = 32°C - 15°C = 17°C.

Substituting the calculated and given values into the formula, we get q = (210 g)(0.235 J/g°C)(17°C) = 826.95 joules. Therefore, the energy required to heat the cube of silver from 15°C to 32°C is about 828 Joules.

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At the final equilibrium temperature, the specific heat capacity of the metal is 5.999 J/g°C.

Given the following data:

To find the specific heat capacity of the metal:

Mathematically, quantity of heat is given by the formula;

[tex]Q = mc\theta[/tex]

Where:

The quantity of heat lost by the water = The quantity of heat gained by the metal.

[tex]Q_{lost} = Q_{gained}\\\\mc\theta = mc\theta\\\\20(4.18)(29.2 - 22.1) = 5.10c(48.6 - 29.2)\\\\83.6(7.1) = 5.10c(19.4)\\\\593.56 = 98.94c\\\\c = \frac{593.56}{98.94}[/tex]

Specific heat capacity of metal, c = 5.999 J/g°C

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The oxidation numbers of nitrogen in NH₄⁺, NO₂, and NaNO₃  are -3, +4, and +5, as determined by balancing the charges of other atoms in the compounds.

The oxidation numbers of nitrogen in NH₄⁺, NO₂, and NaNO₃ can be calculated using some simple rules. In NH₄⁺, nitrogen must balance the charge from the four hydrogen atoms, each having an oxidation number of +1, leading to the oxidation number of nitrogen being -3. For NO₂, oxygen typically has an oxidation number of -2, with two oxygen atoms that would contribute an overall charge of -4, thus nitrogen must have an oxidation number of +4 to balance out and make the molecule neutral. Finally, in NaNO₃, with sodium having an oxidation number of +1, and three oxygen atoms giving a total of -6, nitrogen must have an oxidation number of +5 to balance the overall charge to zero due to the monatomic sodium ion.

Therefore, the respective oxidation numbers of nitrogen in NH₄⁺, NO₂, and NaNO₃ are -3, +4, and +5.

Answer: The correct answer is Option D.

Explanation:

A balanced equation follows Law of conservation of mass. This law states that mass can neither be created nor be destroyed but it can only be transformed from one form to another. In a chemical reaction, mass is always conserved.

This also states that the total number of individual atoms on the reactants side must be equal to the total number of individual atoms on the product side.

For the given chemical reaction:

[tex]2CH_4+4O_2\rightarrow CO_2+4H_2O[/tex]

On the reactant side:

Number of Carbon atoms = 2

Number of Hydrogen atoms = 8

Number of Oxygen atoms = 8

On the product side:

Number of Carbon atoms = 1

Number of Hydrogen atoms = 8

Number of Oxygen atoms = 4

In order to balance the number of atoms, 2 must be added infront of [tex]CO_2[/tex] molecule, in order to balance the equation.

Hence, the correct answer is Option D.

Answer: the ionic compound calcium fluoride [tex](CaF_2)[/tex]

Explanation:

[tex]\Delta T_f=i\times k_f\times m[/tex]

[tex]T_f[/tex] = change in freezing point

i = Van'T Hoff factor

[tex]k_f[/tex] = freezing point constant

m = molality

1. For [tex]C_{12}H_{22}O_{11}[/tex] , i= 1 as it is a non electrolyte and does not dissociate.

2. For [tex]MgSO_{4}[/tex] , i= 2 as it is a electrolyte and dissociate to give 2 ions.

[tex]MgSO_4\rightarrow Mg^{2+}+SO_4^{2-}[/tex]

3. For [tex]LiCl[/tex], i= 2 as it is a electrolyte and dissociate to give 2 ions.

[tex]LiCl\rightarrow Li^{+}+Cl^{-}[/tex]

4. For [tex]CaF_{2}[/tex], i= 3 as it is a electrolyte and dissociate to give 3 ions.

[tex]CaF_2\rightarrow Ca^{2+}+2F^{-}[/tex]

Thus as vant hoff factor is highest factor for [tex]CaF_{2}[/tex] and the freezing point will be lowest.

Answer:

After the well-known solids, liquids, and gases, plasmas are considered as the fourth state of matter. They are found rarely on Earth, however, they are found in enormous quantity all through the universe. As they comprise free-flowing charged particles, plasmas exhibit many specific features.  

In the majority of the plasmas, the electrons and protons take place in equal numbers, forming it electrically neutral. As they flow liberally, they are influenced by magnetic and electric fields in the manner not witnessed in the other forms of matter. These fields can affect plasmas over higher distances, warping, pinching, and modeling them, like the twisting flares observed on the Sun's surface.  

A 1 molal solution of NaCl would have a lower boiling point elevation than a 1 molal solution of MgCl₂, because NaCl dissociates into fewer ions than MgCl₂, resulting in a lower can't Hoff factor.

The question asks which 1 molal solution has a higher boiling point compared to a 1 molal solution of MgCl₂. The boiling point elevation of a solution is affected by the number of solute particles in the solution, which is related to the can't Hoff factor (i), the measure of ion dissociation of a solute. Since MgCl₂, FeCl₂, CaCl₂, and BaCl₂ all dissociate into three ions (1 cation and 2 anions) when dissolved in water, their boiling point elevation would be expected to be similar given equai molal solutions. However, NaCl dissociates into two ions, thus a 1 molal solution of NaCl would have a lower boiling point elevation compared to a 1 molal solution of MgCl₂ due to lower i value.

0.479 g of hydrogen will be produced if 25 grams Zn are reacted with 17.5 grams HCl.

Hydrochloric acid is an aqueous solution of hydrogen gas and chlorine gas.

The reaction is

[tex]\rm Zn + 2 HCl = ZnCl2 + H_2[/tex]

The number of moles present in Zn will be  

[tex]\rm \dfrac{25g}{65.38g/mol} = 0.3824 mol[/tex]

The number of moles present in HCl will be

[tex]\rm \dfrac{ 17.5g}{36.46g/mol} = 0.479mol[/tex]

The mass of hydrogen present is  [tex]\rm 0.479mol \times 1/2 \times 2g/mol = 0.479g[/tex]

Thus, The correct option is B. 0.479 g.

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To produce a solution that is 35.0 wt% SrCl2 with 36.0 grams of SrCl2, one would need to add 66.9 grams of water. This is because the total weight of the solution is the weight of SrCl2 plus the weight of the water needed.

In order to determine how much water must be added to 36.0 g of SrCl2 to produce a solution that is 35.0 wt% SrCl2, we must understand that the 35% by weight represents that 35 g of SrCl2 is in 100 g of the solution. Thus, to find the total weight of the water and the SrCl2, we should set up the equation 36g (weight of SrCl2) / X g (total weight of solution) = 35%, which would give that X = 102.9 g. The total solution weight is the weight of the SrCl2 plus the weight of the water needed, so to find the weight of the water we subtract the weight of SrCl2 (36 g) from the total weight of solution (102.9 g), which gives us 66.9 g as the amount of water to be added to the SrCl2.

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