Answer:
Let's just say that, for whatever reason, you wanted to build your very own live version of Benedict Cumberbatch, from all the chemical elements that make up the British heartthrob. It would cost you precisely $151,578.46 US ($198,166.10 Cdn) — excluding labour, according to author Bill Bryson.
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Explanation:
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Answer:
6.574 g NaF into 300ml (0.25M HF) => Bfr with pH ~3.5
Explanation:
For buffer solution to have a pH-value of 3.5 the hydronium ion concentration [H⁺] must be 3.16 x 10⁻⁴M ( => [H⁺] = 10^-pH = 10⁻³°⁵ =3.16 x 10⁻⁴M).
Addition of NaF to 300ml of 0.25M HF gives a buffer solution. To determine mass of NaF needed use common ion analysis for HF/NaF and calculate molarity of NaF, then moles in 300ml the x formula wt => mass needed for 3.5 pH.
HF ⇄ H⁺ + F⁻; Ka = 6.6 x 10⁻⁴
Ka = [H⁺][F⁻]/[HF] = 6.6 x 10⁻⁴ = (3.16 x 10⁻⁴)[F⁻]/0.25 => [F⁻] = (6.6 x 10⁻⁴)(0.25)/(3.16x10⁻⁴) = 5.218M in F⁻ needed ( = NaF needed).
For the 300ml buffer solution, moles of NaF needed = Molarity x Volume(L)
= (5.218M)(0.300L) = 0.157 mole NaF needed x 42 g/mole = 6.574 g NaF needed.
Check using the Henderson - Hasselbalch Equation...
pH = pKa + log ([Base]/[Acid]); pKa (HF) = 3.18
Molarity of NaF = (6.572g/42g/mole)/(0.300 L soln) = 0.572M in NaF = 0.572M in F⁻.
pH = 3.18 + log ([0.572]/[0.25]) ≅ 3.5.
One can also back calculate through the Henderson -Hasselbalch Equation to determine base concentration, moles NaF then grams NaF.
Halogens can be characterized as :
1) High Electronegativity
2) Low melting & boiling points
3) Forms Ionic compounds
4) Non-metallic in nature
Hope this helps!
Answer:
D
Explanation:
Because the number of protons is the same as the atomic number, we know what the number of protons has to be 26. The mass number, 55, is the same as the number of protons plus neutrons. Lastly, because there is no charge on this atom, the number of electrons would have to be the same as the number of protons, which is 26.
