which of the following statements correctly describe protecting groups? select all statements that apply. multiple select question. a reactive functional group is converted into another functional group that does not interfere with the desired reaction. when the oh group of an alcohol is reacted with tbdmscl/imidazole the resulting tbdms ether is known as a protecting group. protecting groups must be easily removed (deprotection) to regenerate the original functional group.

The range of dilution factors that are needed to set up a successful BOD5 test for this wastewater sample is between 18 and 20.

What is Dilution?

Dilution is the process of adding solvent to a solution to decrease the concentration of solutes within the solution. In this process, the volume of the solution increases while the total amount of solute remains constant.

BOD5 = (Initial DO - Final DO) x Dilution Factor

180 mg/L = (Initial DO - 2 mg/L) x Dilution Factor

Initial DO = 180 mg/L / Dilution Factor + 2 mg/L

We want the initial DO to be between 6 and 8 mg/L, so:

6 mg/L ≤ 180 mg/L / Dilution Factor + 2 mg/L ≤ 8 mg/L

Subtracting 2 mg/L from all parts of the inequality, we get:

4 mg/L ≤ 180 mg/L / Dilution Factor ≤ 6 mg/L

Multiplying all parts by Dilution Factor, we get:

720 mg/L ≤ 180 / Dilution Factor x Dilution Factor ≤ 1080 mg/L

Simplifying, we get:

720 mg/L ≤ 180 x 5 / BOD5 ≤ 1080 mg/L

Dividing by 180 and multiplying by 5, we get:

20 ≤ 5 / BOD5 ≤ 30

Inverting the inequality, we get:

1/30 ≤ BOD5/5 ≤ 1/20

Simplifying, we get:

0.0333 ≤ BOD5/5 ≤ 0.05

Therefore, the range of dilution factors needed to set up a successful BOD5 test for this sample is between 20 and 30.

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The total number of moles of solute (HCl) in 0.50 L of 3.0 M HCl is 1.5 moles.

To determine the total number of moles of solute in a solution, we can use the formula:

moles of solute = concentration of solution x volume of solution

In this case, we are given that the volume of the solution is 0.50 L and the concentration of the solution is 3.0 M HCl.

Using the formula above, we can calculate the number of moles of HCl in the solution:

moles of HCl = 3.0 M x 0.50 L

moles of HCl = 1.5 moles

This result can be explained by the fact that the concentration of a solution is defined as the amount of solute (in moles) per unit volume of the solution (in liters).

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The concentration of [tex]Ca(OH)_2[/tex] is 0.0217 M.

The balanced chemical equation for the reaction between the  [tex]Ca(OH)_2[/tex] and the HCl is:

[tex]Ca(OH)_2 + 2HCl[/tex] → [tex]CaCl_2 + 2H_2O[/tex]

From this equation, we can see that 1 mole of [tex]Ca(OH)_2[/tex] reacts with 2 moles of HCl.

The number of moles of HCl used can be calculated as:

moles HCl = Molarity * Volume in liters[tex]= 0.029 M\ *\ 0.0373 L = 0.0010837\ mol[/tex]

Since the stoichiometry of the reaction is 1:2 between [tex]Ca(OH)_2[/tex] and HCl, the number of moles of [tex]Ca(OH)_2[/tex] in the 25.0 mL sample can be calculated as:[tex]moles\ Ca(OH)2 = 0.0010837\ mol / 2 = 0.00054185\ mol[/tex]

The concentration of [tex]Ca(OH)_2[/tex] can then be calculated as:

[tex]Molarity = moles[/tex] ÷ [tex]Volume\ in\ liters\ = 0.00054185\ mol[/tex] ÷ 0.025 L = 0.0217M

Therefore, the concentration of [tex]Ca(OH)_2[/tex] is 0.0217 M.

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You would need 740.1 grams of oxygen to completely react with 254 grams of tristearin, C₅₇H₁₁₀O₆, in the given reaction.

To find out how many grams of oxygen are needed to completely react with 254 g of tristearin, C₅₇H₁₁₀O₆, in the given reaction, follow these steps:

1. Calculate the molar mass of tristearin (C₅₇H₁₁₀O₆) and oxygen (O₂).
2. Convert grams of tristearin to moles using its molar mass.
3. Use stoichiometry to find the moles of oxygen needed.
4. Convert moles of oxygen to grams using its molar mass.

Molar mass of tristearin: (57 * 12.01) + (110 * 1.01) + (6 * 16.00) = 891.62 g/mol
Moles of tristearin: 254 g / 891.62 g/mol = 0.285 moles
Moles of oxygen needed: 0.285 moles * (163 O₂ / 2 C₅₇H₁₁₀O₆) = 23.16 moles
Molar mass of O₂: 2 * 16.00 = 32.00 g/mol
Grams of oxygen needed: 23.16 moles * 32.00 g/mol = 740.1 g

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The final pressure of the gas when the volume changes from 720 mL to 820 mL is approximately 1.22 atm.


To solve this problem, we can use Boyle's Law, which states that the product of the initial pressure and volume (P1V1) is equal to the product of the final pressure and volume (P2V2) for a gas at a constant temperature:

P1V1 = P2V2

Given the initial pressure (P1) is 1.4 atm and the initial volume (V1) is 720 mL, we need to find the final pressure (P2) when the volume (V2) changes to 820 mL. Rearrange the formula to solve for P2:

P2 = P1V1 / V2

Substitute the given values:

P2 = (1.4 atm × 720 mL) / 820 mL
P2 ≈ 1.22 atm

Therefore, the final pressure of the gas is approximately 1.22 atm.

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The rate enhancement that could be accomplished by the enzyme forming one low barrier hydrogen bond with transition state at 25 °C is 10⁷.

The decrease is about 5.7 kJ/mol that is observed in the free energy of the activation of the reaction when the 10 fold increase will occurs in the rate of the reaction at 25ºC.

The hydrogen bond  free energy = 40 kJ/mol.

Now, for the hydrogen bond, the times of the  10 fold increase

= (40 kJ/mol) / (5.7 kJ/mol)

= 7 times.

Hence, the rate that show the 10 fold increase 7 times. Therefore, the enhancement in the rate will be 10⁷.

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This question is incomplete, the complete question is :

calculate the rate enhancement that could be accomplished by an enzyme forming one low barrier hydrogen bond with transition state at 25 °C.

This is because when water is added to ethanol, the two substances form a homogenous solution, meaning the two substances mix together to form a single molecular solution.

As a result, the water molecules and ethanol molecules take up the same amount of space, meaning the total volume of the mixture is less than the sum of the original two volumes (50 ml of water + 50 ml of ethanol = less than 100 ml).

This phenomenon is known as "volume contraction" and is caused by the intermolecular forces between water and ethanol molecules. This contraction also occurs when two other liquids are mixed together in certain combinations.

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The  three general exceptions to the octet rule is:

The octet rule is  described as a chemical rule of thumb that reflects the theory that main-group elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas.

The structure of the octet is usually held responsible for the relative inertness of the noble gases and the chemical behavior of certain other elements.

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Answer: To determine the pressure change of a gas when it is heated at constant volume, we can use the ideal gas law:

PV = nRT

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

Since the volume of the gas is constant, we can simplify the equation to:

P/T = nR/V

The quantity nR/V is a constant, which means that P/T is also a constant at constant volume. Therefore, we can use the following equation to calculate the pressure at a new temperature:

P2/T2 = P1/T1

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

We can convert the temperatures to Kelvin by adding 273.15:

T1 = 30.0 °C + 273.15 = 303.15 K

T2 = 40.0 °C + 273.15 = 313.15 K

We can plug in the given values and solve for P2:

P2/313.15 K = 2.50 atm/303.15 K

P2 = (2.50 atm)(313.15 K)/(303.15 K)

P2 = 2.58 atm

Therefore, the pressure of the gas increases from 2.50 atm to 2.58 atm when it is heated from 30.0 °C to 40.0 °C at constant volume.

Explanation:

The effect of increased temperature on the rate of dissolution of a solid solute is; Increased temperature increases the rate of dissolution of a solid solute. Option A is correct.

This is because at higher temperatures, the kinetic energy of the solvent molecules increases, leading to more frequent and more energetic collisions with the solute particles. This increased kinetic energy can overcome the intermolecular forces holding the solute together, leading to more rapid dissolution.

The rate of dissolution refers to how quickly a solute dissolves in a solvent to form a homogeneous solution. It is usually expressed as the amount of solute that dissolves per unit time, typically in grams per second or moles per minute.

Hence, A. is the correct option.

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1. 2 moles of Calcium 8016 grams = 8.01x103 grams, 2. 3 moles of Sodium 69 grams = 2.07x1023 particles, and many more given below:

Calcium is an essential mineral that is found in the human body. It is necessary for the proper functioning of many organs, including the heart and muscles. Calcium is also important for the formation and maintenance of healthy bones and teeth. It plays a role in nerve and muscle function, blood clotting, and hormone secretion. Adequate calcium intake is important for both children and adults to ensure proper growth, development, and overall health.

3. 392 grams of Technetium = 9.10x1022 particles

4. 3.01x1024 particles of Chromium = 8.41x10-2 moles

5. 5 moles of Fluorine = 25 grams

6. 24 grams of Helium = 4.67x1023 particles

7. 1.806x1024 particles of Sulfur = 4.86x10-2 moles

8. 3 moles of Platinum = 195.2 grams

9. 240 grams of Argon = 6.67x1023 particles

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The Ksp of NaCl when it begins to crystallize out of a 6.07 M solution is approximately 36.84.

To calculate the Ksp of NaCl in this solution, follow these steps:
1. Identify the balanced dissociation equation: NaCl(s) ↔ Na+(aq) + Cl-(aq).
2. Since NaCl dissociates into a 1:1 ratio, the concentrations of Na+ and Cl- are equal to the initial concentration, 6.07 M.
3. Determine the Ksp expression: Ksp = [Na+][Cl-].
4. Substitute the concentrations into the expression: Ksp = (6.07)(6.07) ≈ 36.84.

In this scenario, the Ksp value represents the point at which NaCl begins to crystallize from the solution. The Ksp increases as more solute precipitates, which reflects the equilibrium between dissolved and solid NaCl.

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we need 5.65 mL of a 6.00 M HCl solution to react with excess Fe2O3 to produce 16.5 g of FeCl3.

The balanced chemical equation for the reaction between Fe2O3 and HCl is:

Fe2O3 + 6 HCl → 2 FeCl3 + 3 H2O

We can use the given mass of FeCl3 to calculate the number of moles of FeCl3 produced:

mass of FeCl3 = 16.5 g
molar mass of FeCl3 = 162.2 g/mol
moles of FeCl3 = mass/molar mass = 16.5 g / 162.2 g/mol = 0.1017 mol

From the balanced chemical equation, we see that the stoichiometry between HCl and FeCl3 is 6:2, which simplifies to 3:1:

3 HCl → 1 FeCl3

Therefore, we need one-third as many moles of HCl as moles of FeCl3:

moles of HCl = 1/3 × moles of FeCl3 = 0.0339 mol

Now we can use the definition of molarity to calculate the volume of 6.00 M HCl solution needed:

moles of HCl = M × V
V = moles of HCl / M

V = 0.0339 mol / 6.00 mol/L = 0.00565 L

Finally, we can convert the volume to milliliters:

0.00565 L × 1000 mL/L = 5.65 mL

Therefore, we need 5.65 mL of a 6.00 M HCl solution to react with excess Fe2O3 to produce 16.5 g of FeCl3.
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The expected effects on the people if the alpine and the tidewater glaciers melted is the melting the glaciers add to the rising sea levels.

The melting glaciers add to the rising sea levels, which in the turn will increases the coastal erosion and the elevates storm to surge the warming air and the ocean temperatures that will create the more frequent and the intense coastal storms such as the hurricanes and the typhoons.

The glaciers has been the melting for the decades because of the climate warming and therefore the monitoring of it is very important. The melting of the alpine and the tidewater glacier rises the sea level.

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Answer:To find the number of CO2 molecules in a 0.25 g sample of dry ice, we can use the Avogadro's number and the molar mass of CO2.The molar mass of CO2 is:12.01 g/mol (C) + 2(16.00 g/mol) (O) = 44.01 g/molThis means that 1 mole of CO2 contains 6.022 x 10^23 molecules.To find the number of moles in 0.25 g of CO2, we can use the molar mass:0.25 g / 44.01 g/mol = 0.005681 molFinally, we can use Avogadro's number to find the number of CO2 molecules:0.005681 mol x 6.022 x 10^23 molecules/mol = 3.422 x 10^21 CO2 moleculesTherefore, a 0.25 g sample of dry ice contains approximately 3.422 x 10^21 CO2 molecules.

7.3 mL of NaOH are used to titrate the 10.00 mL aliquot.

The balanced equation for the reaction between NaOH and HCl is:

NaOH(aq) + HCl(aq) → H₂O(l) + NaCl(aq)

To calculate the volume of NaOH used,  determine how much HCl is left after it reacts with the CaCO₃, and then how much NaOH is required to neutralize that remaining HCl.

Step 1: Calculate the moles of HCl used to react with CaCO₃

The balanced equation for the reaction between CaCO₃ and HCl is:

CaCO₃(aq) + 2HCl(aq) → CaCl₂(aq) + H2O(l) + CO₂(g)

From the balanced equation, we can see that 1 mole of CaCO₃ reacts with 2 moles of HCl. Therefore, the number of moles of HCl used to react with the CaCO₃ is:

moles HCl = (7.50 mL)(2.00 mol/L) = 0.015 mol

Step 2: Calculate the concentration of HCl in the 125.0 mL solution

Started with 7.50 mL of 2.00 M HCl, which is equivalent to 0.015 moles of HCl. We added enough water to make a 125.0 mL solution, so the concentration of HCl in the solution is:

C = moles of HCl / volume of solution in L

C = 0.015 mol / 0.125 L = 0.12 M

Step 3: Calculate the moles of HCl remaining in the 10.00 mL aliquot

moles NaOH = moles HCl remaining in aliquot

(C of NaOH)(volume of NaOH) = (C of HCl)(moles of HCl remaining in aliquot)

(0.058 mol/L)(volume of NaOH) = (0.12 mol/L)(moles of HCl remaining in 10.00 mL aliquot)

moles of HCl remaining in 10.00 mL aliquot = moles of HCl in 125.0 mL solution - moles of HCl used to react with CaCO₃

moles of HCl remaining in 10.00 mL aliquot = (0.12 mol/L)(0.125 L) - 0.015 mol = 0.0035 mol

Substituting this into the equation gives:

(0.058 mol/L)(volume of NaOH) = (0.12 mol/L)(0.0035 mol)

volume of NaOH = (0.12 mol/L)(0.0035 mol) / (0.058 mol/L) = 0.0073 L

Step 4: Convert the volume of NaOH to mL

volume of NaOH = 0.0073 L x (1000 mL / 1 L) = 7.3 mL

Therefore, 7.3 mL of NaOH are used to titrate the 10.00 mL aliquot.

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152 grams of [tex]C2H6[/tex]would release 152 kJ of energy when it condenses at its boiling point.

Assuming you meant "[tex]C2H6[/tex]" instead of "[tex]CH Ch[/tex]", the heat of vaporization of [tex]C2H6[/tex]is 30.1 kJ/mol. The molar mass of [tex]C2H6[/tex] is 30.07 g/mol.

To calculate the heat of vaporization for 152 g of [tex]C2H6[/tex], we need to first calculate the number of moles of [tex]C2H6[/tex]:

152 g / 30.07 g/mol = 5.05 mol

Then, we can calculate the energy released using the heat of vaporization:

5.05 mol x 30.1 kJ/mol = 152 kJ

Therefore, 152 grams of [tex]C2H6[/tex]would release 152 kJ of energy when it condenses at its boiling point.

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A greater speed of particles in a container will lead to an increase in temperature, pressure, potential phase changes, and possibly container expansion if the container is not rigid.

If there is a greater speed of particles in a container, the following changes will occur:

1. Increase in temperature: Faster-moving particles will have greater kinetic energy, which will result in an increase in the temperature of the system.

2. Increase in pressure: As the particles move faster, they will collide more frequently with the walls of the container, exerting a greater force. This leads to an increase in pressure.

3. Potential phase change: If the increase in temperature is significant enough, a phase change may occur, such as a solid melting into a liquid or a liquid evaporating into a gas.

4. Expansion of the container (if not rigid): If the container is not rigid, the increased pressure may cause it to expand or deform.

To summarize, a greater speed of particles in a container will lead to an increase in temperature, pressure, potential phase changes, and possibly container expansion if the container is not rigid.

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(a) The entropy of the system would increase. The transition from a liquid to a gas state involves an increase in the number of microstates, which leads to an increase in entropy. Therefore, the entropy of the system will increase as [tex]CH3OH[/tex] transitions from a liquid state to a gas state.

(b) The entropy of the system would increase. The reaction involves the formation of three molecules of gas from one molecule of gas and another molecule that contains two molecules of gas. The increase in the number of molecules leads to an increase in the number of microstates, which results in an increase in entropy.

(c) The entropy of the system would increase. The transition from a solid to a liquid or gas state involves an increase in the number of microstates, which leads to an increase in entropy. Therefore, the entropy of the system will increase as [tex]2KCIO3[/tex] transitions from a solid state to a liquid or gas state.

(d) The entropy of the system would increase. The reaction involves the formation of two molecules of gas from three molecules of gas and one molecule of aqueous substance. The increase in the number of molecules leads to an increase in the number of microstates, which results in an increase in entropy.

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Steam turbine will do 150 J more useful work

Given the efficiency of both a steam turbine (40.0%) and a steam engine (25.0%), we can calculate the amount of useful work each device can do when provided with 1000 J of thermal energy.

For the steam turbine:
Efficiency = (Useful work output) / (Input energy)
0.4 = (Useful work output) / (1000 J)
Useful work output = 0.4 * 1000 J = 400 J

For the steam engine:
Efficiency = (Useful work output) / (Input energy)
0.25 = (Useful work output) / (1000 J)
Useful work output = 0.25 * 1000 J = 250 J

Now, we can find the difference in useful work between the two devices:
Difference = Useful work (steam turbine) - Useful work (steam engine)
Difference = 400 J - 250 J = 150 J

So, the steam turbine will do 150 J more useful work than the steam engine when provided with 1000 J of thermal energy.

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The molality of a solution formed by mixing 104 g. Of silver nitrate(AgNO₃) with 1. 75 kg of water is 0.350 mol/kg.

The molality of a solution formed by mixing 104 g of silver nitrate (AgNO₃) with 1.75 kg of water can be calculated as follows:

1. First, convert the mass of silver nitrate to moles:

104 g AgNO₃ * (1 mol AgNO₃/169.87 g AgNO₃) = 0.6122 mol AgNO₃

2. Then, calculate the mass of water in kilograms:

1.75 kg water = 1750 g water

3. Finally, divide the moles of AgNO₃ by the mass of water in kilograms to get the molality:

molality = 0.6122 mol AgNO₃ / 1.75 kg water = 0.350 mol/kg

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Set of coefficients that will balance the chemical equation is: A. 1,5,3,4

Combustion is a chemical reaction that occurs when fuel combines with oxidant to produce heat and light. The fuel is a hydrocarbon, such as methane or propane, while oxidant is oxygen from the air. During combustion, hydrocarbon is oxidized to produce carbon dioxide and water vapor, releasing energy in form of heat and light.

The balanced chemical equation for the combustion of propane is: C₃H₈ (g) + 5O₂ (g) → 3CO₂ (g) + 4H₂O (l)

So the correct set of coefficients to balance equation is option A: 1, 5, 3, 4.

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The mass of KI that must be dissolved in 500 g of water to produce a 0.05 M solution of KI is approximately 8.3 grams. The answer is C) 8.3 grams.

To calculate the mass of KI required to make a 0.05 M solution, we need to use the formula for freezing point depression:

ΔT = K_f × m

where ΔT is the freezing point depression, K_f is the freezing point depression constant of water (1.86 °C/m), and m is the molality of the solution (moles of solute per kilogram of solvent).

Since we want to make a 0.05 M solution of KI, we need to find the molality of the solution. 0.05 moles of KI per liter of solution corresponds to 0.05 moles of KI per 1000 g of water, since the density of water is 1 g/mL. Therefore:

m = 0.05 moles KI / 0.5 kg water = 0.1 mol/kg

Now we can use the freezing point depression formula to find ΔT:

ΔT = K_f × m = 1.86 °C/m × 0.1 mol/kg = 0.186 °C

This means that the freezing point of the solution will be lowered by 0.186 °C compared to pure water.

To calculate the mass of KI required, we can use the formula:

moles of solute = mass of solute / molar mass of solute

Since we want 0.05 moles of KI, we can rearrange this formula to solve for the mass of KI:

mass of KI = moles of KI × molar mass of KI

The molar mass of KI is 166 g/mol. Substituting the given values, we get:

mass of KI = 0.05 mol × 166 g/mol = 8.3 g

Therefore, the mass of KI that must be dissolved in 500 g of water to produce a 0.05 M solution of KI is approximately 8.3 grams. The answer is C) 8.3 grams.

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The total KJ of heat that would be released is B. -83.5 kJ

When a something in a liquid or semi-liquid freezes, it undergoes a phase change to a solid state, and this process involves a release of heat.

For example, when water freezes, it releases 333.5 kJ of heat per kg of water that freezes

To be able to calculate the heat released, we need to use the formula:

q = m x Lf

But first, we must convert grams to kg

m = 250 g x (1 kg / 1000 g) = 0.25 kg

q = 0.25 kg x 333.5 kJ/kg

q = 83.375 kJ

The answer is turned to the negative since heat is released.

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A sample of helium gas that occupies 2.65 L at 1.20 atm would exert a pressure of 3.18 atm in a 1.50-L container at the same temperature, according to Boyle's Law.

To know the pressure exerted by a sample of helium gas that occupies 2.65 L at 1.20 atm when it's compressed to 1.50 L at the same temperature, using Boyle's Law (V₁P₁ = V₂P₂).

Here's the step-by-step explanation:
1. Identify the initial volume (V₁), initial pressure (P₁), and final volume (V₂):
  V₁ = 2.65 L
  P₁ = 1.20 atm
  V₂ = 1.50 L

2. Apply Boyle's Law to find the final pressure (P2):
  V₁P₁ = V₂P₂

3. Plug in the values and solve for P₂:
  (2.65 L)(1.20 atm) = (1.50 L)P₂

4. Calculate P₂:
  P₂= (2.65 L × 1.20 atm) / 1.50 L
  P₂= 3.18 atm
A sample of helium gas that occupies 2.65 L at 1.20 atm would exert a pressure of 3.18 atm in a 1.50-L container at the same temperature, according to Boyle's Law.

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Christina can conclude that Substance A will float.

Part A: Substance A will float.

Part B: To determine which substance will float, we need to compare their densities with the density of water. Density is defined as mass per unit volume. We can calculate the density of each substance by dividing its mass by its volume:

Density of Substance A = 4 g / 6 mL = 0.67 g/mL
Density of Substance B = 8 g / 6 mL = 1.33 g/mL
Density of Substance C = 10 g / 6 mL = 1.67 g/mL

The density of water is approximately 1 g/mL. A substance will float if its density is less than the density of water. In this case, Substance A has the lowest density (0.67 g/mL), which is less than the density of water, so it will float. Substance B and Substance C have densities greater than the density of water, so they will sink. Therefore, Christina can conclude that Substance A will float.

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You need to add 0.405 moles of CH₃NH₃Cl to 200.0 mL of 0.500 M CH₃NH₂ to create a buffer with a pH of 11.

To find the moles of CH₃NH₃Cl needed, you'll need to use the Henderson-Hasselbalch equation and the given information.

The Henderson-Hasselbalch equation is pH = pKa + log([A⁻]/[HA]).

First, calculate pKa using the given Kb value for CH₃NH₂:

pKa = -log(Ka)

= -log(Kw/Kb)

= -log(1.0 × 10⁻¹⁴ / 4.4 × 10⁻⁴)

= 10.36.

Then, plug in the desired pH (11) and the given concentrations of CH₃NH₂ (0.500 M):

11 = 10.36 + log([CH₃NH₃Cl]/[0.500]).

Solving for [CH₃NH₃Cl], you get [CH₃NH₃Cl] = 0.405 M.

Finally, multiply this concentration by the volume of the solution in liters (0.200 L) to find the moles of CH₃NH₃Cl needed: 0.405 M × 0.200 L = 0.405 moles.

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The dilution formula is a mathematical expression used to calculate the final concentration of a solution after it has been diluted.

The formula is:

C1V1 = C2V2

where:

C1 = the initial concentration of the solution

V1 = the initial volume of the solution

C2 = the final concentration of the solution

V2 = the final volume of the solution

1) 250 * 10 = 0.5 * v2

v2 = 5000 mL

2) 400 * 15 = 2000 *c2

c2 = 3M

3) 50 * 20 = 1000 * c2

c2 = 1 M as shown

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