A sample contains 2.2 g of the radioisotope niobium-91 and 15.4 g of its daughter isotope, zirconium-91. how many half-lives have passed since the sample originally formed?

Which question cannot be explained by chemistry? A. How does yeast make bread dough rise? B. Why does sugar dissolve faster in hot water? C. How does a convection oven cook food? D. Why do peeled apples turn brown in air?

Acidic solutions contain high concentrations of a. hydrogen ions b. hydroxide ions c. water

Which gas is found in high percentages in the atmosphere in all of the gas giants?

If your periodic table has the old-style numbering (1A, 2A, etc), what's the easiest way to tell how many valence electrons an element has? A. The number of valence electrons is the same as the column number. B.

Ribosome functions of a organelle and a location of the organelle

How does heat transfer takes place between any two systems?

Hydrate name of CaCl2 * 8 H2O

Calculate the heat evolved from a mixture of 14.1 l of sulfure dioxide

Which stament best describes a solution

Which answer accurately describes the difference between speed and velocity? Read each answer choice carefully. Question 4 options: A. If speed is constant, then velocity is also constant. B. Speed requires direction.