After three half-lives, what fraction of a radioactive sample remains.

Give the formula for the alkyne containing 40 hydrogens

Which group has 4 valence electrons

Calculate the molar mass of NaNCO3

What was one important discovery that the Curies made? A material's radioactivity cannot be changed by altering the material physically. A material's radioactivity can be weakened or intensified by changing it chemically.

Recommend an element use to fill bottles that contain ancient paper. the element should be a gas at room temperature, should be denser than helium, and should not easily react with other elements.

A battery is constructed based on the oxidation of magnesium and the reduction of cu2+. the initial concentrations of mg2 + and cu2 + are 1.2*10-4 m and 1.44 m, respectively, in 1.0-liter half-cells. how long can the battery deliver 5.

A buffer solution is made that is 0.417 M in and 0.417 M in. If for is, what is the pH of the buffer solution? pH = Write the net ionic equation for the reaction that occurs when 0.120 mol is added to 1.00 L of the buffer solution.

BaCl2 (aq) + AgNO3 (aq) → Express your answer as a chemical equation. Enter noreaction if no precipitate is formed.

Make a list of physical changes and chemical changes that you observe or see effects of in the school

Which equation obeys the law of conservation of mass? H2 (g) + O2 (g) → H2O (g) H2 (g) + O2 (g) → H2O (g) + 4He (g) 2H2 (g) + O2 (g) → 2H2O (g) H2 (g) → H2O (g) H2 (g) + O2 (g) → 2H2O (g)