A sample of a radioactive isotope initially contains 20 x 10^10 atoms. After 16 days, 5 x 10^10 atoms remain. what is the half-life of the isotope?

A) 12 days

B) 20 days

C) 10 days

D) 16 days

E) 8 days

Ben and Jerry added small pieces of magnesium to hydrochloride acid. They noticed that bubbles formed, the test tube got hot, and the the magnesium disappeared. What is a sign that a chemical reaction has taken place in this experiment

A sample of fuel is found to contain 87.4% nitrogen and 12.6% hydrogen. if the molecular mass of the fuel is 32.05 grams/miles, what is the molecular formula of the fuel?

Identify the atom that is oxidized, reducing agent, in the following equation: Zn (s) + H2SO4 (aq) - -> ZnSO4 (aq) + H2 (g)

A gas sample with a volume of 5.3 l has a pressure of 735 mm hg at 28 c. What is the sample if the volume remains at 5.3 l but the temperature rises to 86 c

Sickle-cell anemia is a disease of the red blood cells. A person who carries one sickle-cell gene is physically normal, but has the potential to pass on the sickle-cell trait to his or her offspring.

When does a spring tide take place? At the beginning of spring Only during the spring season Only after spring is over At any time

The highest cloud are known as

What is the mass of 4.85 X 10^22 atoms of iron (Fe) ?

If element x has 95 protons how many electrons does it have

Which of the following when dissolved in deionized water would make a good conducting solution? a) methanolb) sugarc) baking soda