The half-life of silver-105 is approximately 41.3 days. Step 2 of 3 : How much of a 12 gram sample of silver-105 would remain after 57 days? Round to three decimal places.

1. The element copper has naturally occurting isotopes with mass numbers of 63 and 65 . The relative abundance and atomic masses are \( 69.2 \% \) for a mass of 62.93 ami and \( 30.8 \% \) for a mass of 64.93 amu. Calculate the average atomic mass of copper.

When excess nitric acid reacts with 1.71 g of iron, 842 mL of hydrogen gas is collected over water. If the barometric pressure is 713 mmHg and the temperature of the water is \( 34^{\circ} \mathrm{C} \), what is the calculated value of R , in atmL/molK? (Water vapor pressure at \( 34^{\circ} \mathrm{C}=39.90 \mathrm{mmHg} \) ) __Fe(s) \( +\ldots \mathrm{HNO}_{3}(\mathrm{aq}) \rightarrow \) _Fe( \( \left.\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+\ldots \mathrm{H}_{2}(\mathrm{~g}) \)

2. Soaps often contain sodium stearate. (Stearate is a complex ion de- rived from fatty acids or fat.) If a precipitate forms when soap is dissolved in hard water (water containing \( \mathrm{Ca}^{2+} \) and \( \mathrm{Mg}^{2+} \) ions), what ion from the soap would you expect to find in the precipitate? Why? (Making predictions)

1. Balance the following electrochemical equation and determine the Emf of the cell, Show all the steps ( 20 marks) NB: Refer to the reduction potential Table in your notes for half cell voltage pp16. \( \left.\mathrm{MnO}_{4}^{2-\mathrm{aq}}\right)+\mathrm{PbSO}_{4}(\mathrm{~s}) \longrightarrow \mathrm{Mn}^{2+}(\mathrm{aq})+\mathrm{Pb}(\mathrm{s})+\mathrm{SO}_{4}^{2-}(\mathrm{aq}) \)

The element copper has naturally occurring isotopes with mass numbers of 63 and 65 he relative abundance and atomic masses are \( 69.2 \% \) for a mass of 62.93 amu and 30.89 nass of 64.93 amu. Calculate the average atomic mass of copper.