2. Sulfuric acid has a molar mass of \( 98 \mathrm{~g} / \mathrm{mol} \). In the laboratory there is 100 mL of a 0.20 M sulfuric acid solution. How much water needs to be added to this volume to prepare a solution containing \( 4.9 \mathrm{~g} / \mathrm{L} \) of sulfuric acid?

5. Compare For each of the given elements, list two other elements with similar chemical properties, \( \begin{array}{ll}\text { a. iodine (II) } & \text { b. barium (Ba) }\end{array} \)

c. A partir de una solución 5 M de cloruro de sodio ( NaCl ) se realizaron tres diluciones seriadas con factor de dilución \( 1 / 5 \). Calcula la concentración de cada dilucion en \( \% \mathrm{~m} / \mathrm{v} \).

2. Find \( \Delta \mathrm{H}^{\circ} \) for the reaction \( 2 \mathrm{H}_{2}(\mathrm{~g})+2 \mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(\mathrm{l}) \), using the following thermochemical data. \( \begin{array}{ll}\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(\mathrm{l})+2 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{CO}_{2}(\mathrm{~g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) & \Delta \mathrm{H}=-875 \mathrm{~kJ} \\ \mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g}) & \Delta \mathrm{H}=-394.51 \mathrm{~kJ} \\ \mathrm{H}_{2}(\mathrm{~g})+1 / 2 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) & \Delta \mathrm{H}=-285.8 \mathrm{~kJ}\end{array} \)

Strontium-90 is a radioactive material that decays according to the function \( A(t)=A_{0} e^{-0.0244 t} \), where \( A_{0} \) is the initial amount present and \( A \) is the amount present at time \( t \) (in years). Assume that a scientist has a sample of 800 grams of strontium-90. (a) What is the decay rate of strontium-90? (b) How much strontium- 90 is left after 40 years? (c) When will only 200 grams of strontium-90 be left? (d) What is the half-life of strontium-90? (a) The decay rate of strontium- 90 is \( \square \% \). (Type an integer or a decimal. Include the negative sign for the decay rate.)

Strontium-90 is a radioactive material that decays according to the function \( A(t)=A_{0} e^{-0.0244 t} \), where \( A_{0} \) is the inifial amount present and \( A \) is the amount present at time \( t \) (in years). Assume that a scientist has a sample of 800 grams of strontium- 90 . (a) What is the decay rate of strontium- 90 ? (b) How much strontium- 90 is left after 40 years? (c) When will only 200 grams of strontium- 90 be left? (d) What is the halt-life of strontium- 90 ?