Answer:
Snape must wave his wand 8 times.
Explanation:
To determinate the concentration of a final solution that was prepared to mix different solutions of the same solute, we can use the equation:
C1V1 + C2V2 + ... + CnVn = CFVF
Where C is the concentration, V is the volume, 1, 2..., n refer for the different solutions, and F refers tho the final solution.
C1 = 0.3 and V1 = 2000 mL
There will be n solution with C = 0.75 and V = 25 mL, then :
0.3x2000 + n(0.75 x 25) = 0.34VF
VF is the final volume, which must be the sum of all the solutions:
VF = 2000 + 25n. Then:
600 + 18.75n = 0.34 ( 2000 + 25n)
600 + 18.75n = 680 + 8.50n
18.75n - 8.50n = 680 - 600
10.25n = 80
n = 80/10.25
n = 7.80
So, Snape must wave his wand 8 times (7 times will not achieve 34%).
Answer:
- <em>1. The mass of an atom is concentrated at the nucleus.</em>
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- <em>3. Positive charge is condensed in one location within the atom.</em>
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- <em>4. The majority of the space inside the atom is empty space.</em>
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- <em>6. The atom contains a positively charged nucleus.</em>
Explanation:
When J.J Thmpson discovered the electron, he depicted the atom by the plum pudding model: a solid dough of homogeneously distributed positive charge (the pudding) containing negatively charged electrons (the plums).
Later, the scientist <em>Ernest Rutherford</em>, with its experiment of the gold foil experiment showed that the subatomic particles where not all concentrated in a solid part.
When a thin gold foil was bombarded with alpha particles (positively charged nuclei of helium atoms), most of the particles went through the gold sheet, with little deviation, but some particles bounded with a high deviation.
Such few high deviations were explained by the fact that there was a heavy region in the atom (the core or nucleus) with the positive charge that repelled the positively charged alpha particles.
Thus, <em>the mass of the atom was conentrated at the nucleus</em> (choice 1), where the positive charge is distributed in one location, which is the nucleus (not over the entire atom, just on the nucleus) discarding the choice number 2 (that a positive charge is spread equally over the atom) and proving choices 3 (<em>the positive charge is condensed in one location within the atom</em>) and 6 (<em>the atom contains a positively charged nucleus</em>).
Since most of the particles indeed went through the nucleus, this nucleus has to occupy little space, and most of the atom was empty space, proving choice 4 (<em>the majority of the space inside the atom is empty space</em>).
Ok first, we have to create a balanced equation for the dissolution of nitrous acid.
HNO2 <-> H(+) + NO2(-)
Next, create an ICE table
HNO2 <--> H+ NO2-
[]i 0.230M 0M 0M
Δ[] -x +x +x
[]f 0.230-x x x
Then, using the concentration equation, you get
4.5x10^-4 = [H+][NO2-]/[HNO2]
4.5x10^-4 = x*x / .230 - x
However, because the Ka value for nitrous acid is lower than 10^-3, we can assume the amount it dissociates is negligable,
assume 0.230-x ≈ 0.230
4.5x10^-4 = x^2/0.230
Then, we solve for x by first multiplying both sides by 0.230 and then taking the square root of both sides.
We get the final concentrations of [H+] and [NO2-] to be x, which equals 0.01M.
Then to find percent dissociation, you do final concentration/initial concentration.
0.01M/0.230M = .0434 or
≈4.34% dissociation.
Wavelength decreases as frequency increases.
Imagine a heart rate graph. As the heart beats faster, frequency increases and the time between heartbeats decreases (wavelength).
<span>Make sense that way?</span>