Achemistry graduate student is given 500. ml of a 0.20 m chloroacetic acid (hch2clco2) solution. chloroacetic acid is a weak acid with ka= 1.3 x 10^-3. what mass of kch2clco2 should the student dissolve in the hch2clco2 solution to turn it into a buffer with ph = 3.01? you may assume that the volume of the solution doesn't change when the kch2clco2 is dissolved in it. be sure your answer has a unit symbol, and round it to 2 significant digits.

12 g of choloracetic acid

Explanation:

The buffer equilibrium is:

HCH₂ClCO₂ ⇄ CH₂ClCO₂⁻ + H⁺

pka= -log ka =

Ka: 1,3x10⁻³ = [CH₂ClCO₂⁻] [H⁺] / [HCH₂ClCO₂]

By Henderson-Hasselbalch equation:

pH = pka + log₁₀ [A⁻] / [HA]

3,01 = 2,89 + log₁₀ [A⁻] / [HA]

1,318 = [A⁻] / [HA]

As molar concentration of chloroacetic acid (HA) is 0,20M

[A⁻] = 0,26 mol/L

The volume is 500 mL ≡ 0,5 L

0,26mol/L × 0,5 L = 0,13 moles of chloroacetic acid. In grams:

0,13 mol × (94,5g / 1mol) = 12 g of choloracetic acid

I hope it helps!

3

explanation:

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.