How many of the following are compounds?

H2O, N2O4, NaOH, MnO2, HF

Cobalt fluoride crystallizes in a closest packed array of fluoride ions, with the cobalt ions filling one-half of the octahedral holes. What is the formula of this compound?

A substance can be pure: when a substance has unique properties through which it can be distinguished when a substance has common properties through which it can be identified when a substance can be separated into two different groups of material

Structurally, what is the difference between the dermis and the epidermis? A. the dermis contains more types of tissue. B. the epidermis consists of mostly adipose cells. C. the epidermis is thicker. D. the dermis is made of mostly dead cells

0.0400 M solution of HClO2, pH = 1.80 solve for Ka

Evaporation occurs at the surface of a liquid. Which particles of the liquid will evaporate?

Does a mole of hydrogen have the same mass as a mole of oxygen? explain your answer.

A 0.500-L sample of H₂SO₄ solution was analyzed by taking a 100.0mL aliquot and adding mL of. After the reaction occurred, an excess of ions remained in the solution. The excess base required mL of for neutralization.

Ammonia can be prepared by the reaction of magnesium nitride with water. The products are ammonia and magnesium hydroxide. Write and balance the equation.

Which period is the shortest in the long form of the periodic table? Name all the elements in this period.

A mole of gas at 0.0oC and 760. torr occupies 22.4 L. What is the volume of this gas at 25. oC and 760. torr