What is the mass of naoh that would have to be added to 500 ml of a solution of 0.20 m acetic acid in order to achieve a ph of 5.0?

The correct answer is 2.5 g.

Let x be the mass of NaOH in grams

The molar mass of NaOH = 40.0 gms/mol

Moles of NaOH = mass / molecular mass of NaOH

= x grams / 40.0 gms /mol = 0.025 x mol

Initial moles of CH₃COOH = volume × concentration of CH₃COOH

= 500 / 1000 × 0.20 = 0.1 mol

CH₃COOH + NaOH ⇒ CH₃COONa + H2O

Moles of CH₃COOH left = initial moles of CH₃COOH - moles of NaOH = 0.1 - 0.025x mol

Moles of CH₃COONa formed = moles of NaOH = 0.025x mol

Henderson-Hasselbalch equation:

pH = pKa + log ([CH₃COONa] / [CH₃COOH])

= pKa + log (moles of CH₃COONa /moles of CH₃COOH)

5.0 = 4.76 + log [0.025a / (0.1 - 0.025a)]

log [0.025a / (0.1 - 0.025a)] = 0.24

0.025a / (0.1 - 0.025a) = 10^0.24 = 1.738

0.068445a = 0.17378

a = 0.17378 / 0.068445

= 2.54 g

Mass of NaOH = a = 2.54 g or 2.5 g

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

the correct answer is b. a strong acid completely dissociates to its ions when dissolved in water. completely dissociates to and ions. a is incorrect because does not fully ionize to and ions and some remain as the compound . c and d are incorrect because, and do not fall into the category of bronsted lowry acids. a bronsted lowry acid is a proton donor and since both molecules do not have a proton to donate they are not bronsted lowry acids. likewise,   if we use the lewis acid definition, they cannot be acids. a lewis acid is an electron pair acceptor. both and have a complete octet so can not accept any electrons which disqualifies them as acids.