An original sample of the radioisotope fluorine-21 had a mass of 80.0 milligrams. Only 20.0 milligrams of this original sample remain unchanged after 8.32 seconds. What is the half-life of fluorine-21?

(1) 1.04 s (3) 4.16 s

(2) 2.08 s (4) 8.32 s

In a chemical equation, what do the coefficients indicate?

A patient needs to take her cholesterol medication every morning and night. Her prescription bottle most likely says

Gold has a specific heat of 126 J / (kg! K). A sculptor increased the temperature of a 0.5 kg block of gold by 10°C. How much energy did the sculptor add to the gold?

Describe What is happening to particles of a material in heat energy is transferred to the material in the temperature increases

Which choice contains a FALSE statment? A. For the vaporization of liquid benzene ΔH is positive. B. For the formation of 1 mol nitrogen dioxide from its elements (heat is absorbed) ΔH is negative. C.

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?