2) A uniform deposit of 10.0 grams of silver is needed to completely coat a meta

Question

2) A uniform deposit of 10.0 grams of silver is needed to completely coat a metal spoon with silver. How long ( in minutes) would a current of 12.0 A have to be passed through a solution of AgNOs to silver-coat the metal spoon ? 3) A particular first-order reaction has a rate constant of 1.35 102 s-1 at 25.0 °C. What is the magnitude of k at 75.0 °Cif Ea-55.3 kJ/mol? 4) The half-life for beta decay of strontium-90 is 28.8 years. A milk sample is found to contain 10.3 ppm strontium-90. a) How many years would pass before the strontium-90 concentration would drop to 1.0 ppm? b) Write the balanced equation for the radioactive decay of strontium-90, and identify the deca product. 12

Explanation / Answer

4.

Half life, t1/2 = 28.8 years

Rate constant, k = ln(2) / t1/2 = 0.024 yr-1

Co = 10.3 ppm

a)

C = 1 ppm

C = Co exp(-k t)

1 = 10.3 exp(-0.024 t)

10.3 = exp(0.024 t)

t = 97 years

b)

Strontium-90 undergoes decay into yttrium-90

9038Sr --> 9039Y + 0-1 + ve

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