What indicates that an area in the northern hemisphere is experiencing summer?

The molar mass of iron(fe) is 55.8 g/mol. what is the mass in grams of 2.25 moles of iron?

Calculate the h3o+ concentration in a solution of acetic acid if the concentration of molecular acetic acid present at equilibrium is 9.97x10-3 m and k for the dissociation is 1.86x10-5. ch3cooh(aq)+h2o(l)+> h3o+(aq)+ch3coo-(aq) show me how to get the answer.

Someone do this for me. im really stuck