Chemistry, 29.03.2020 04:25 starfox5454

How many grams of cobalt (II) nitrate, Co(NO3)2, are required to make a 2.20%(w/v) aqueous solution in a 250 mL volumetric flask?

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Answer from: benjamenburton1

$\large \boxed{\text{5.50 g}}$

Explanation:

Percent means " per hundred," so % m/V means the grams of something in 100 mL of volume.

$\text{m/V \%} = \dfrac{\text{mass of solute} }{\text{volume of solution}} \times 100 \, \%$

Data:

m/V % = 2.20 %

V of solution = 250 mL

Calculations:

$\text{2.20 \%} = \dfrac{\text{mass of solute} }{\text{250 mL}} \times 100 \, \%\\\\\text{Mass of solute} = \dfrac{2.20\, \% \times \text{250 mL}}{100 \%} = \text{5.50 g}\\\\\text{The mass of Co(NO$_{3}$)$_{2}$ is $\large \boxed{\textbf{5.50 g}}$}$

Answer from: Quest

the ozone layer acts as a filter for the shorter wavelength and highly hazardous ultraviolet radiation (uvr) from the sun, protecting life on earth from its potentially harmful effects. when the sky is clear, there is an inverse relationship between stratospheric ozone and solar uvr measured at the earth's surface.

Answer from: Quest

remember that hf is only the energy of one photon. not two. not three. one. 1) 5.12 * 10^3 photons find the energy of one photon, then determine how many photons are needed to reach the sensitivity. e = hf = (6.626 * 10^-34 js)(5.95 * 10^19 hz) = 3.94247 * 10^-14 j per photon (2.02 * 10^-10 j) / (3.94247 * 10^-14 j/photon) = 5123.69149 photons round to three sig figs. 2) 5.77 * 10^-17 j energy of pulse = energy per photon * number of photons = hfn = (6.626 * 10^-34 js)(1.66 * 10^13 hz)(5250) = 5.774559 * 10^-17 j round to three sig figs. 3) 4.07 * 10^8 kj/mol 10^12 pm = 1 m c = fλ f = c/λ e = hf = hc/λ = [(6.626 * 10^-34 js)(3.00 * 10^8 m/s) / (2.94 * 10^-12 m)](1 kj/1000 j)(6.02 * 10^23 photons/mol) = 40702571.4 kj/mol round to three sig figs. 4) 9.94 * 10^-1 m e = hc/λ λ = hc / e = (6.626 * 10^-34 js)(3.00 * 10^8 m/s) / (2.00 * 10^-25 j) = 0.9939 m round to three sig figs. 5) 9.06 * 10^3 photons energy of pulse = energy per photon * number of photons number of photons = energy of pulse / energy per photon = energy of pulse / (hf) = (3.87 * 10^-13 j) / [(6.626 * 10^-34 js)(6.45 * 10^16 hz)] = 9055.23695 photons round to three sig figs. 6) 2.78 * 10^-15 j this is problem 1, except in reverse. sensitivity = minumum number of photons * energy per photon = (5930)(6.626 * 10^-34 js)(7.077 * 10^14 hz) = 2.78070758 × 10^-15 j round to three sig figs.

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How many grams of cobalt (II) nitrate, Co(NO3)2, are required to make a 2.20%(w/v) aqueous solution...

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