The half-life of strontium-90 is 28 years. how long will it take a 52 mg sample to decay to a mass of 13 mg?

An atom has the following electron configuration. 1s22s22p63s23p4s23d3 How many valence electrons does this atom have?

How much heat energy must be absorbed to completely melt 35.0 grams of H2O (s) at 0°C? (1) 9.54 J (3) 11 700 J (2) 146 J (4) 79 100 J

Define what does phase is

What group will group 16 most likely bond with?

What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M NH₃ with 25.00 mL of 0.10 M NH₄Cl? Assume that the volume of the solutions are additive and that Kb = 1.8 * 10⁻⁵ for NH₃. Enter your answer in exponential (E) format (sample 1.

When magnesium combines with oxygen, the reaction involves a. a conversion of protons into electrons. b. sharing of electrons between Mg and O. c. transfer of electrons from Mg to O. d. transfer of electrons from O to Mg.

The activation energy for the reaction no2 (g) + co (g) ⟶no (g) + co2 (g) is ea = 100 kj/mol and the change in enthalpy for the reaction is δh = - 375 kj/mol.

What process transform solar energy into chemical energy?

When the reaction was carried out the calculated theoretical yield for water was 176 grams but the measured yield was 148 grams what is the percent yield

For an atom's electrons, how many energy sublevels are present in the principal energy level n = 4?