What is the coefficient for potassium in the balanced equation

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation:

About 3% of the water on earth is freshest. only about 40% of that freshwater is available for human use. why is so much freshwater unavailable for human use?

Imagine one batch of soup (batch “a”) is made with 8.19 g/can of salt, according to the recipe, and a second batch of soup (batch “b”) is made with 8.32 g/can of salt. explain which batch would be more resistant to frost damage if it is shipped a great distance in winter and explain why.