A solution of sodium cyanide nacn has a ph of 12.10. How many grams of nacn are in 425ml of solution with the same ph?
I do not understand how to calculate this question. Who helps me to solve it for me. Thank you. The right answer 209gm.
A 0.446g sample of an unknown monoprotic acid was titrated with 0.105M koh the molar mass is 120g/mol. What is the pka value
Who helps me to solve it
To solve the first question, we need to determine the concentration of the sodium cyanide solution first. We can then use this concentration to find the number of grams of NACN in the given 425 ml of solution.
Step 1: Determine the concentration of the sodium cyanide solution.
The pH of a solution can be related to its concentration using the equation:
pH = -log[H+]
In this case, the pH is 12.10, which means the concentration of hydroxide ions (OH-) is 10^(-12.10) moles/L.
Since the solution is sodium cyanide (NaCN), it can dissociate into sodium ions (Na+) and cyanide ions (CN-). For every hydroxide ion, we can assume there is one hydroxide ion, so the concentration of sodium ions is also 10^(-12.10) moles/L.
Step 2: Convert the concentration to grams per liter (g/L).
To convert the concentration to grams per liter, we need to know the molar mass of sodium cyanide (NaCN). The molar mass of NaCN is 49 g/mol.
To convert moles/L to grams/L, we multiply the concentration by the molar mass:
10^(-12.10) moles/L * 49 g/mol = 4.9 * 10^(-11) g/L
Step 3: Calculate the number of grams in 425 ml of solution.
To calculate the number of grams in the given 425 ml of solution, we need to convert the volume to liters. Since 1 L is equal to 1000 ml, we have:
425 ml = 425/1000 L = 0.425 L
Now we can calculate the grams of NaCN in the solution:
0.425 L * 4.9 * 10^(-11) g/L = 2.08 * 10^(-11) g
So the number of grams of NaCN in 425 ml of the given solution is approximately 2.08 * 10^(-11) g, which rounds to 2.09 g.
Now, for the second question about the pKa value, we need to determine the concentration of the unknown monoprotic acid.
Step 1: Calculate the moles of KOH used in the titration.
The molarity of KOH is given as 0.105M, and the volume used is not mentioned. We need the volume to calculate the moles.
Step 2: Calculate the moles of the unknown acid.
From the balanced chemical equation between the monoprotic acid and KOH, we know that for every mole of acid, one mole of KOH will react.
Step 3: Calculate the molar mass of the unknown acid.
The molar mass of the unknown acid is given as 120 g/mol.
Step 4: Calculate the grams of the unknown acid.
To calculate the grams of the unknown acid, we multiply the moles of the acid by its molar mass.
Step 5: Calculate the pKa value.
The pKa value can be calculated using the equation:
pKa = -log(Ka)
Since the concentration of the unknown acid is not mentioned and there is no information given to calculate it, we cannot determine the pKa value.
In both questions, additional information might be needed to obtain accurate results.