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3 years ago

what is the kinetic energy of the emitted electrons when cesium is exposed to uv rays of frequency 1.4×1015hz?

1 answer:

7 0

The equation you used is KE=hv-hv0, where h=6.63*10^-34 (constant). You multiply h by 1.5*10^15. Multiply h by the threshold freq of cesium (from part A). Subtract the second answer from the first answer, and you get the kinetic energy. Hope this helps.

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PLZ I NEEEEEEEDDDDDD HELP

MrRa [10]

Answer:

2h+02=h20

Explanation:

2 in front of h on left side

2 in front of h on right side

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3 years ago

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Why does naphthalene have a higher melting point than biphenyl?

AlexFokin [52]

Naphthalene has a higher melting point than biphenyl because naphthalene is a polar compound while biphenyl is a non-polar compound. Studies show that polar compounds have higher melting and boiling points than nonpolar compounds. It is because polar compounds have strong intermolecular forces.

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3 years ago

What can natural selection accomplish? prove Darwin's idea of "survival of the fittest" change relative number of inhabitants wi

oksian1 [2.3K]

Natural selection makes it so that an organism from a species has a better chance of surviving than an organism in the same species, but with different traits. Survival of the fittest proves that certain traits can help an organisms survive better than its peers. For example, say there was an allele that made bears have thicker fur than others. The year-round climate is extremely cold. The bears with thicker fur are more likely to survive due to the warmth their fur provides and will have more offspring. The bears with thinner fur will die more often and not produce healthy offspring due to the frigid temperature. Eventually, the allele for thin fur will die out because the bears with these alleles cannot survive in their habitat.

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3 years ago

A student who is performing this experiment pours an 8.50 mL sample of the saturated borax solution into a 10 mL graduated cylin

gtnhenbr [62]

Answer:

ksp = 0,176

Explanation:

The borax (Na₂borate) in water is in equilibrium, thus:

Na₂borate(s) ⇄ borate²⁻(aq) + 2Na⁺(aq)

When you add just borax, the moles of Na²⁺ are twice the moles of borate²⁻, that means 2borate²⁻=Na⁺ (1)

The ksp is defined as:

ksp = [borate²⁻] [Na⁺]²

Then, borate²⁻(B₄O₇²⁻) reacts with HCl thus:

B₄O₇²⁻ + 2HCl + 5H₂O → 4H₃BO₃ + 2Cl⁻

The moles of HCl that reacts with B₄O₇²⁻ are:

0,500M×0,01200L = 6,00x10⁻³ mol of HCl

As two moles of HCl react with 1 mol of B₄O₇²⁻, the moles of B₄O₇²⁻ are:

6,00x10⁻³ mol of HCl× $\frac{1molB_{4}O_{7}^{2-}}{2molHCl}$ = 3,00x10⁻³ mol of B₄O₇²⁻

For (1), moles of Na⁺ are 3,00x10⁻³ mol ×2 = 6,00x10⁻³ mol of Na⁺

The [borate²⁻] is 3,00x10⁻³ mol of B₄O₇²⁻/0,00850L = 0,353M

And [Na⁺] is 6,00x10⁻³ mol of Na⁺ / 0,00850L = 0,706M

Replacing in the expression of ksp:

ksp = [0,353] [0,706]²

ksp = 0,176

I hope it helps!

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ss7ja [257]

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