Radium-226 is a common isotope on earth, but it has a half-life of about 1620 years. given that earth is some 5 billion years old, why is there any radium at all?

If a 1.00M aqueous NaCl solution has a density of 1.01g/mL, what is the concentration in mass percent? 5.79% 58.44% 1.00% 99.0%

Which of the following describes an endothermic reaction? Thermal energy is released by the system. Thermal energy is absorbed by the surroundings. Thermal energy is absorbed by the system. Thermal energy is not transferred.

Which of the following pairs of elements is/are likely to form an ionic bond? Choose one or more: A. Na and F B. Ca and Cl C. H and H D. Cl and Br E. K and I F. N and C

If the concentration of h2 is doubled, will the reaction rate quadruple, double, or remain the same?

12. A sample of sulfur dioxide gas found deep inside a volcanic crater has a volume of 3500. ML at a temperature of 200.00C and a pressure of 250. KPa. Calculate the number of moles present in the crater.

What is the solubility of m (oh) 2 in a 0.202 m solution of m (no3) 2? ksp 4.45*10^-12?

Describe three physical changes that occur in nature.

Name the two sub-atomic particles in the nucleus of an aluminium atom.

Identify the true statement. Choose one: A. The expansion of ice sheets at the end of the Pleistocene caused glacial rebound in northern Canada. B. Regions covered by glacial ice are termed periglacial environments. C.

What is the concentration when 0.065 moles of NaNO3 are dissolved in enough water to make 150.0 mL of solution?