What mass in grams of potassium fluoride is needed to make 150.0 mL of a 0.450 M hydrofluoric acid/fluoride buffer with a pH of 4.25 from 1.25 M HF and solid potassium fluoride?  The Ka for HF is 6.8×10–4.

A chemistry graduate student is given 250. mL of a 0.10M methylamine (CH3NH2) solution. Methylamine is a weak base with K 4.4 x 10 CH3NH2Br should the student dissolve in the CH3NH2 solution to turn it into a buffer with pH = 10.21? What mass of You may assume that the volume of the solution doesn't change when the CH3NH3Br is dissolved in it. Be sure your answer has a unit symbol, and round it to 2 significant digits. 0 ☐ x10 X G

For humans to maintain the pH of their blood close to 7.4, the body uses three buffer systems: carbonate, phosphate and proteins. If the pH of the blood goes below 6.8 or above 7.8, death may result. Imagine you want to make a phosphate buffer in the lab that resembles the bloods phosphate buffer. You start by mixing 0.95 M NaH2PO4 and 0.68 M Na2HPO4. H2PO4-  + H2O ⇌  HPO42-  + H+  pKa= 7.21  (5 marks total) a. From the reaction above indicate the weak acid and the conjugate base involved in making this buffer. (2 marks) b. Calculate the pH of the phosphate buffer solution. Provide your answer with 2 decimal places (2 marks) c. If the pH calculated in b. was the blood pH of an actual patient, would you say this patient’s blood pH is in the normal range or are they suffering from alkalosis or acidosis? (1 mark)

Which of the following aqueous mixtures will result in a buffer with a pH higher than 7.0? (For HCNO, Ka = 2.2×10-4, for NH3, Kb = 1.8×10-5 ) 10 mL of 0.1 M NH3 + 10 mL of 0.1 M HCl   10 mL of 0.1 M HCNO + 5.0 mL of 0.1 M NaOH   10 mL of 0.1 M HCNO + 10 mL of 0.1 M NaOH   10 mL of 0.1 M NH3 + 5.0 mL of 0.1 M HCl   10 mL of 0.1 M NH3 + 10 mL of 0.1 M HCNO

How many grams of dry NH4Cl need to be added to 2.50 L of a 0.300 M solution of ammonia, NH3 , to prepare a buffer solution that has a pH of 8.74? Kb for ammonia is 1.8×10−5 . (Please type answer no write by hend)

Consider a buffer made by adding 132.8 g of NaC₇H₅O₂ to 300.0 mL of 2.35 M HC₇H₅O₂ (Ka = 6.3 x 10⁻⁵) a What is the pH of this buffer?     b What is the pH of the buffer after 0.750 mol of H⁺ have been added?     c What is the pH of the buffer after 0.250 mol of OH⁻ have been added?

You have been given 0.200 Molar solutions of hydrocyanic acid and potassium cyanide. The Ka of HCN = 4.9x10-10. If you wanted to make a buffer with a pH = 9.00, would you add a greater volume of the HCN solution or the KCN solution?  More HCN equal amounts of each more KCN

How many grams of ammonium chloride must be added to 0.53 L of 1.7 M ammonia to prepare a pH = 10.01 buffer? (See the Acid-Base Table.)

9 If the dissociation constant of a weak acid is 1.4 x 10-5, at what ratio should you adjust the concentration of the weak acid and its conjugate base in order to prepare a buffer that has a pH of 4.85? a) 0.100 M weak acid with 0.0100 M conjugate base b) 0.0100 M weak acid with 0.100 M conjugate base c) 0.100 M weak acid with 0.200 M conjugate base d) 0.300 M weak acid with 0.300 M conjugate base e) 0.500 M weak acid with 0.250 M conjugate base