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.
Answer:
First Method: Vacuum Distillation and Chromatographic separation of the remains that were precipitated out from the peel.
Second Method: Extraction of components from orange peels by help of precipitation procedures that are mostly done <em>In Situ. </em>Those components can be recovered using the saponification process. Then these are examined under UV light spectroscopy. Now, the existence and extent of carotenoids can be determined by checking the levels of anti-oxidants.
Answer:
8.912x10^-18
Explanation:
-dn/dt = pANa/2piMRT
100 g = initial copper
Number of moles = 100/63.546
= 1.5736
Mass of copper left = 100-10.0168
= 89.9832
Moles = 89.9832/63.546
= 1.4160
dn = 1.4160-1.5736
= -0.1576
dt = 2 hrs
A = 3.23mm² = 3.23x10^-6
M = 63.546
T = 0.0821
T = 1508k
Na = 6.023x10²³
When we insert all these into the formula above
We get
P = 8.912x10^-18atm
Answer:
8) 45 volt
9) 8 ohms
100 volt
Explanation:
using ohms law all through
8) v = 3×15
9) R= 120/15
the last V=100×1
Answer:
1. light is made up of energy
2. light travels in a straight line
3. the speed of light is exactly 299 792 km per second
4. this is the speed when light is traveling in a vacuum and not obstructed by the atmosphere 5. traveling at the speed of light you could go around the earth seven and a half times in a second
6. light can move super fast super slow and not at all
7. we can use light to weigh Stars
8. we can use light as tweezers
9. bubbles can turn sound into light
10. lasers can make things cold
