1. Indicate the concentration of each ion present in the solution formed by mixi

Question

1. Indicate the concentration of each ion present in the solution formed by mixing the following. (Assume that the volumes are additive.)

(a) 40 mL of 0.100 M HCl and 10.0 mL of 0.410 M HCl

H+
________ M

Cl -
________ M


(b) 15.0 mL of 0.285 M Na2SO4 and 21.4 mL of 0.200 M KCl

Na+
________ M

K+
________ M

SO42-
________ M

Cl -
_________ M


(c) 3.50 g of NaCl in 48.4 mL of 0.444 M CaCl2 solution
Na+
_______ M

Ca2+
________ M

Cl -
________ M

__________ J/hr

3. Write condensed electron configurations for the following atoms and ions, using appropriate noble-gas core abbreviations. Put superscripted electron count numbers in parentheses. For example the electron configuration for Fe is [Ar]4s(2)3d(6).

(a) Te = ______

(b) Cr = ______

(c) Ba = _______

(d) Ge = ______

(e) V = _____

Explanation / Answer

1. Indicate the concentration of each ion present in the solution formed by mixing the following.

(Assume that the volumes are additive.)

(a) 40 mL of 0.100 M HCl and 10.0 mL of 0.410 M HCl
HCl = H+ + Cl-
H+ = Cl- = (40*0.1+10*0.41)/(40+10) = 0.162 M

(b) 15.0 mL of 0.285 M Na2SO4 and 21.4 mL of 0.200 M KCl
Na2SO4 + KCl = 2Na+ + SO4(2-) + K+ + Cl(-)

Na+ = 2*15*0.285/(15+21.4) = 0.235 M

K+ = 21.4*0.2/(15+21.4) = 0.1176 M

SO42- = 15*0.285/(15+21.4) = 0.117 M

Cl - = 21.4*0.2/(15+21.4) = 0.1176 M

(c) 3.50 g of NaCl in 48.4 mL of 0.444 M CaCl2 solution

Molar mass of NaCl, MW = 58.45 gm/mol
no of moles of NaCl, n = W/MW = 3.5/58.45 = 0.06 moles
Volume of solution, V = 48.4 ml= 0.0484 L

Molarity of Na+ = n/V = 0.06/0.0484= 1.24 M

NaCl + CaCl2 = Na+ + Ca(2+) + 3Cl-

Na+ = 1.24 M

Molarity of Ca(2+ )= 0.444 M

Cl - = 1.24+2*0.444 = 2.128M

2. A stellar object is emitting radiation at 1870 nm. A detector is capturing 7E7 photons per second

at this wavelength. h = 6.63E-34 J-s. c = 2.998E8 m/s.

(a) What is the total energy of the photons detected in one second?

wavelength, lambda = 1870 nm = 1.87E-6 m
Energy = n*h*c/lambda = 7E7*6.63E-34*2.998E8/1.87E-6 = 0.744E-11 J/s

(b) What is the total energy of the photons detected in one hour?
one hour = 3600sec
total energy = 0.744*3600 = 2678.6 J/hr

3. Write condensed electron configurations for the following atoms and ions, using appropriate noble-

gas core abbreviations. Put superscripted electron count numbers in parentheses. For example the

electron configuration for Fe is [Ar]4s(2)3d(6).

(a) Te = [Kr]5s(2)4d(10)5p(4)

(b) Cr = [Ar]4s(1)3d(5)

(c) Ba = [Xe]6s(2)

(d) Ge = [Ar]4s(2)3d(10)4p(2)

(e) V =   [Ar]4s(2)3d(3)

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