How is it possible for scientists to do studies about things that happened?

The pH of a solution is 7. Which best describes the solution? The solution has more hydrogen ions than hydroxide ions. The solution has fewer hydrogen ions than hand soap. The solution has the same number of hydrogen ions as apple juice.

Which statement about gases is true

Hydrazine, ammonia, and hydrogen azide all contain only nitrogen and hydrogen. The mass of the hydrogen that combines with 1.00g of each compound is 1.4 x 10^-1g, 2.4x10^-1 g and 2.40x10^-2 respectively.

How many electrons does carbon need to gain to obtain a noble gas electron configuration

What is the pressure of the gas in this mercury manometer if h = 81 mm and atmospheric pressure is 749 mmHg

What is unique about the way that transition metals form compounds? a. They don't form compounds c. They can form bonds with the electrons in the two outer-most shells b. They are the most reactive d. They can donate all of their electrons

What prompted rutherford to do the alpha particle scattering experiment?

How many moles of hydrogen would be required to produce 5.0 mol of water?

What is the biggest difference between an exothermic and endothermic process? A. The direction of energy flow. B. The amount of energy transferred. C. The type of energy being transferred. D. The speed with which energy is transferred.

The mass of 1 mol of chromium (atomic mass 51.996 amu) is