How many significant figures are in the measurement 40, 500 mg? a) two b) three c) four d) five

2. An element's atomic number is the A. number of protons in an atom's nucleus. B. mass of the atom. C. weight of the atom. D. sum of the protons and neutrons in an atom.

An object has a mass of 3.30 and a volume of 0.1063 l what is the density

Write the chemical equation for the equilibrium that corresponds to Ka. Write the chemical equation for the equilibrium that corresponds to.

When sodium is obtained, great care is taken to prevent air coming into contact with sodium. Give a reason for this.

The hydroxide ion concentration of a solution is 0.00001 moles per liter. what is the hydrogen ion concentration, and is the solution acidic or basic

56 Explain, in terms of atomic structure, why the elements in Group 2 have similar chemical properties. 131

What must molecules do to react? a. Molecules must heat up b. Molecules must collide c. Molecules must expand to fill their container d. Molecules must interact with a catalyst

How many pictograms are in a gram?

Which type of signaling pathway uses second messengers because the hormone cannot pass through the plasma membrane? a.) amino acid based b.) lipid based

Why are the gases in the troposphere layer denser than the gases in the other layers?