1. What was the first recorded element to be discovered?

What is the relation between concentration of reactants and the rate of chemical reaction?

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

What is the ph of a solution that has a hydrogen ion concentration of 1.0 * 10 -9 m?