Help with chemistry please

Which chemical reaction involves the most oxygen atoms?

You are making a solution of calcium chloride dissolved in water. you add solid, stir, and it dissolves. you add just a spatula tip full, stir, and the solid does not dissolve. how could you describe the solutions before and after adding the spatula tip amount

Find the number of grams of hcl needed to react completely with .50 moles of magnesium.

Which statement characterizes synthetic polymers? a. they come from animals and plants. b. they are found in nature. c. they are made in a lab. d. they are components of starch.