A radioisotope is placed near a radiation detector, which registers 80 counts per second. Eight hours later, the detector registers 5 counts per second. What is the half - life of the radioactive isotope

A lightbulb filled with argon gas has a volume of 75 milliliters at STP. How many moles of argon gas does the lightbulb contain?

How can you describe the location of vanadium (v, atomic number 23) on the periodic table? Choose all that apply. period 5, group 4 period 4, group 5 nonmetals transition metals

Which molecular compound is composed of the greatest number of atoms? A. Dinitrogen Monoxide B. Sodium Chloride C. Potassium Nitride D. Carbon Dioxide

Which of the following equations represents an exothermic reaction? (Select all that apply.) NH3 (g) + 12.0 kcal ½N2 (g) + 3/2 H2 (g) C (graphite) C (diamond), H = - 0.

Two gases are placed in a sealed flask and allowed to react. Which statement is true about the concentrations of the reactants and products when this closed system reaches dynamic equilibrium? They will be equal and constant.

Andy has two samples of liquids. Sample A has pH of 4, and sample B has a pH of 6. what can Andy conclude about these two samples? Sample A is a neutral b alkali c acidic Sample B is a neutral b alkali c acidic

How does a lone pair contribute to molecular shape? A. It is too small to affect the molecule's shape. B. It takes up space like an "invisible" atom. C. It forces the molecule into a tetrahedral shape. D. It lets the bonding pairs spread out more.

The are of a rectangle is 12 in^2. what is the area in cm^2. there are 2.54cm in an inch.

Which statements describe advantages of models? Check all that apply. Models make it possible to easily notice patterns. Models can be used to communicate and test design ideas. Models allow scientists to predict relationships.

Are energy levels and orbitals the same thing?