Chemistry, 21.05.2021 01:00 caromaybelline71

Solid lead acetate is slowly added to 75.0 mL of a 0.0492 M sodium sulfate solution. What is the concentration of lead ion required to just initiate precipitation?

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Answer from: gogo16732

The concentration of lead ion required to just initiate precipitation is - $2.37\times10^-^5 M$

Explanation:

Lets calculate -:

Solubility equilibrium -: PbI_2(s) ⇄ Pb^2^+ (aq) + 2I^- (aq)

Solubility product of PbI_2 , Q=[Pb^2^+]_i_n_i_t_i_a_l [I^-]^2_i_n_i_t_i_a_l $=9.8\times10^-^9$

Concentration of I^- =[KI]=0.0492M

When the ionic product exceeds the solubility product , precipitation of salt takes place .

$Q_s_p\geq K_s_p$

[Pb^2^+]_i_n_i_t_i_a_l [I^-]^2_i_n_i_t_i_a_l $\geq 9.8\times10^-^9$

[Pb^2^+]_i_n_i_t_i_a_l [0.0492]^2 $\geq 9.8\times10^-^9$

[Pb^2^+]_i_n_i_t_i_a_l $\geq \frac{9.8\times10^-^9}{[0.0492]^2}$

[Pb^2^+]_i_n_i_t_i_a_l $\geq$ $\frac{9.8\times10^-^9}{2.42\times10^-^3}$

[Pb^2^+]_i_n_i_t_i_a_l $\geq$ $2.37\times10^-^5 M$

Thus , PbI_2 will start precipitating when [Pb^2^+]_i_n_i_t_i_a_l $\geq 2.37\times10^-^5 M$ .

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.

Answer from: Quest

Higher temperature = molecules move around faster. and vice versa.

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Solid lead acetate is slowly added to 75.0 mL of a 0.0492 M sodium sulfate solution. What is the con...

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