Simple molarity, buffer question

In summary, the problem involves adding 3.3g of solid NaC2H3O2*3H2O to 46mL of deionized water and 4.0 mL of 6.0M HC2H3O2. The concentration of HC2H3O2 is 0.48M and 9.12 x 10^-3 moles are contained in a 19mL buffer. To destroy the system, the same amount of moles of HCl should be added, which would be 12mL of 2.0M HCl.
  • #1
qpham26
56
0

Homework Statement


this is a part of a buffer solutions problem

3.3g of solid NaC2H3O2*3H2O added to 46mL of deionized water and 4.0 mL of 6.0M HC2H3O2.

a. How many moles of HC2H3O2 are contained in a 19 mL of the above buffer?
b. How many moles of NaOH would need to be added to the 19 mL of buffer to destroy the system? (complete neutralization)
c. How many mL of 2.0 M HCL would be needed to destroy 19 mL of the buffer system?

Homework Equations





The Attempt at a Solution


a. The concentration of HC2H3O2 will be 4x6/50 = 0.48M
moles of HC2H3O2 are contained in a 19ml will be 0.48M x 0.019mL = 9.12 x 10^-3 mols
b. same amount of moles as the acid?

c. clueless.


thanks for your time
 
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  • #2
Think what would be the reaction in c. Question is very similar to b, it is just a matter of realizing what is going on and following the stoichiometry.
 
  • #3
so to completely destroy the buffer system, the amount of HCl should be equal to the number of moles of NaC2H3O2*3H2O?
3.3/(MM of NaC2H3O2*3H2O) = 0.024 moles?
the volume will then be
0.024 mole / 2.0 M = 0.012L = 12mL

is this correct and also were the answer for a and b correct as well?

thanks for your time.
 
  • #4
I have not checked the numbers, but the logic looks OK.
 
  • #5


a. Your calculation for the moles of HC2H3O2 in 19 mL of the buffer is correct.
b. To destroy the buffer system, you would need to add an equal amount of moles of a strong base, such as NaOH. Since the moles of HC2H3O2 in 19 mL of the buffer is 9.12 x 10^-3, you would need to add the same amount of moles of NaOH to neutralize the system.
c. To calculate the volume of 2.0 M HCl needed to destroy 19 mL of the buffer system, you can use the equation M1V1 = M2V2. M1 and V1 represent the concentration and volume of the buffer, and M2 and V2 represent the concentration and volume of the added acid. In this case, M1 = 0.48 M, V1 = 19 mL, M2 = 2.0 M, and V2 is what we are trying to find. Rearranging the equation, we get V2 = (M1V1)/M2 = (0.48 M x 19 mL)/2.0 M = 4.56 mL. Therefore, you would need to add 4.56 mL of 2.0 M HCl to destroy the buffer system.
 

Related to Simple molarity, buffer question

What is molarity?

Molarity is a unit of concentration that measures the number of moles of a solute in a liter of solution. It is expressed in units of moles per liter (mol/L) or sometimes as molar (M).

How do you calculate molarity?

Molarity is calculated by dividing the number of moles of solute by the volume of the solution in liters. The formula for molarity is: Molarity (M) = moles of solute (mol) / volume of solution (L).

What is a buffer solution?

A buffer solution is a solution that resists changes in pH when small amounts of acid or base are added. It is typically made up of a weak acid and its conjugate base, or a weak base and its conjugate acid.

How do you prepare a buffer solution?

To prepare a buffer solution, you need to mix a weak acid or base with its conjugate base or acid in a specific ratio. The ratio will depend on the desired pH of the buffer solution and the pKa of the weak acid or base.

Why are buffer solutions important in scientific experiments?

Buffer solutions are important in scientific experiments because they help maintain a constant pH, which is crucial for many biochemical reactions. They also help to prevent drastic changes in pH when small amounts of acid or base are added, allowing for more accurate and consistent results.

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