For chemical drawings, you can use the Chemical Equation editor in the submission box for the assignment. You can also download a program called Marvin Sketch (https://chemaxon. com/products/marvin). 9. Draw the Lewis structure for sulfur tetrafluoride, SF4, and then draw the electron pair geometry. What’s the name of the molecular shape of sulfur tetrafluoride? Note: You can draw this on paper, take a picture, and paste the picture in your document. 10. Draw the structure of water. Is water considered polar or nonpolar? Why? Note: You can draw this on paper, take a picture, and paste the picture in your document. 11. When someone is injured, responding medical personnel may use either hot packs or cold packs to treat the injuries. These are examples of miniature chemical reactions. Using hot packs and cold packs as an example, explain the terms endothermic reaction and exothermic reaction.
12. Combustion reactions take place between a fuel and oxygen and produce carbon dioxide and water. Balance the following combustion reaction.

13. Aqueous lead (II) nitrate, Pb(NO3)2 undergoes a double displacement reaction with aqueous sodium chloride, NaCl, in which a precipitate forms. If the precipitate contains lead, write the balanced chemical equation for this reaction. Be sure to include the states of each of the reactants and products.
14. Explain the four basic types of chemical reactions. Be sure to include a sample equation for each type. Describe how rate relationships and activation energy are important in chemical reactions.
15. Write the equilibrium expression for the following reaction. Based upon the value of K, would you expect there to be more or less product in the equilibrium mixture? Why?