The number 0.00003009 expressed in exponential notation is

A hydrocarbon has the formula C5H12. What is the percent by mass of carbon in the compound?

Elements that are in the same ________  have a tendency to have very similar properties .

When chlorine undergoes the reaction Cl ® Cl – , which of the following statements is true.

What is the result of the following multiplication expressed in scientific notation to the correct number of significant figures?(2.13 x 108)(7.0 x 10-8)

If you start with 2.0 grams each of N2 and H2, how much NH3 could be produced according to the balanced equation N2(g) + 3 H2(g)–> 2 NH3(g)   (report the answer using 2 significant figures) _______ grams

A 52.8 g gold nugget is dropped into a graduated cylinder containing 50.00 mL of water and the level of the water rises to 52.80 mL. What is the density of the gold? (use the correct number of significant figures) _______ g\mL

A compound has a molar mass of 42.0 g/mol and the emperical formula is CH2{“version”:”1.1″,”math”:”2″}. What is the molecular formula?

What is the formula for hydrobromic aicd _______ .

An unknown element X forms a compound with the formula Al2X3.  X forms an ion that has 36 electrons.  What is the identity of X?  _______ .