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1. Your supervisor asks you to prepare 250.00 mL of ammonium buffer solution (0.15 M) with pH=9.00, from a concentrated ammonia solution (25%w/w, d=0.91g/cm3) and solid ammonium chloride (98% w/w). (MW of NH3 = 17.03 g/mol and FW of NH4Cl = 53.5 g/mol and pKaNH4+/NH3 =9.24).

a) How many milliliters of the concentrated ammonia solution do you need?

b) How many grams of ammonium chloride do you need?

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Related questions

If you needed to perform a reaction in a controlled pH environment that was fairly basic, you might choose to use the ammonium and ammonia buffer system. How many grams of solid ammonium chloride would you have to add to 2.500 liters of 0.190 M NH3 to obtain a buffered solution of pH= 9.45?

(Kb of NH3 = 1.8 * 10^-5)

1)

How many grams of dry NH4Cl need to be added to 2.30 L of a 0.100 M solution of ammonia, NH3, to prepare a buffer solution that has a pH of 8.64? Kb for ammonia is 1.8รƒย—10รขยˆย’5.

Express your answer with the appropriate units.

2)

Part A

a solution that is 0.175 M in HC2H3O2 and 0.120 M in KC2H3O2

Express your answer using two decimal places.

PH=

Part B

a solution that is 0.195 M in CH3NH2 and 0.110 M in CH3NH3Br

Express your answer using two decimal places.

PH=

3)

A buffer contains significant amounts of ammonia and ammonium chloride.

Part A

Write an equation showing how this buffer neutralizes added acid (HNO3).

Express your answer as a chemical equation.

Part B

Write an equation showing how this buffer neutralizes added base (CsOH).

Express your answer as a chemical equation.

4)

Calculate the ratio of CH3NH2 to CH3NH3Cl required to create a buffer with pH = 10.20.

Express your answer using two significant figures.

5)

Buffer capacity depends on two quantities. What are they?

a high concentration of conjugate acid molecules in solution and the pH of the solution
an equal number of conjugate acid and base molecules, and a high concentration of each
how close the buffer is to having a 10:1 ratio of the buffer components, and having a high concentration of the components

the range of pH values over which the solution can act as a buffer, and an equal ratio of conjugate acid to conjugate base

6)

A 1.0-L buffer solution is 0.120 M in HNO2 and 0.160 M in NaNO2.

Part A

Determine the concentrations of HNO2 and NaNO2 after addition of 1.7 g HCl.

Express your answers using three significant figures separated by a comma.

Part B

Determine the concentrations of HNO2 and NaNO2 after addition of 1.7 g NaOH.

Express your answers using three significant figures separated by a comma.

Part C

Determine the concentrations of HNO2 and NaNO2 after addition of 1.7 g HI.

Express your answers using three significant figures separated by a comma.

7)

Why is the molar solubility of silver chloride lower in an aqueous solution of sodium chloride than in pure water?

Why is the molar solubility of silver chloride lower in an aqueous solution of sodium chloride than in pure water?

because the presence of extra chloride ion shifts the equilibrium of the AgCl dissolution reaction toward the undissociated silver chloride
because solubility relies on concentrations of all the species in the dissolution reaction equation, and lower solubility means higher amounts of solid silver chloride
because silver ions and sodium ions form a completely insoluble precipitate and fall out of the solution

because sodium chloride takes up all the water and doesn't leave any interactions for the silver chloride, causing reduced solubility

8)

In which of the following would lead sulfate be most soluble?

In which of the following would lead sulfate be most soluble?

1 M NaNO3
1 M H2SO4
1 M Pb(NO3)2
1 M CuSO4

You are to make 90.0 mL of a 0.27 M buffer at ph 7.20 using the acid form of the Good buffer EPPS (MW = 252.332 g / mol, pKa = 8.00)

Questions:

1. Using the molarity, volume, and molecular weight, calculate how many grams of solid EPPS you need to weigh out?

2. Using the Henderson-Hasselbalch equation and the information given, calculate the value of [A-] / [HA]

3. Using the value of [A-] / [HA] calculated in question 2 and the concentration given at the beginning (Conc.), solve for x in this equation:

[A-] / [HA] = x / (Conc. -x)

4. The unknown x is in units of Molar. Given the volume from the beginning, how many moles of NaOH would this be?

5. Calculate how many mL of a 1 M NaOH solution you would need for the number of moles calculated in the previous question.

When making a buffer using two solutions - one of the conjugate acid, one of the conjugate base - the calculations are very similar.

You are to make 100.0 mL of a 0.50 M acetate buffer ( pKa = 4.72) at ph 5.00 using 0.50 M stocks of acetic acid and sodium acetate

6. Using Henderson-Hasselbalch and the information given, calculate the value of [A-] / [HA]

7. Reuse the equation from questions 3, but in place of Conc. use the final volume (100 mL) of the solution. The unknown (x) is now the volume of base form we need to add. Using [A-] / [HA] calculated in questions 6 and the equation shown, solve for x.

8. If the final volume is the total of the acid and base solutions, how many mL of the acid form do you need to combine with the base form in the previous question?

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