Element A has a half-life of 10 days. A scientist measures out 200 g of this substance. After 30 days has passed, the scientist reexamines the sample.

How much Element A will remain in the sample?

50 g

25 g

12.5 g

100 g

The Bohr atomic model suggests that: The atom is made mostly of space. Electrons randomly orbit the nucleus. Protons and neutrons occupy energy shells. Gamma rays can can be used to split atoms.

What foods contain Nucleic acids?

If I drink two 5 hour energy drinks. Will I have twice the amount of energy for 5 hours or 10 hours of energy?

What is evaporation? Describe what happens at the molecular level during evaporation.

What is the oxidation number of oxygen in H2O2?

Hemoglobin, a protein in red blood cells, carries o2 from the lungs to the body's cells. iron (as ferrous ion, fe2+) makes up 0.33 mass % of hemoglobin. if the molar mass of hemoglobin is 6.8 Ã 104 g/mol, how many fe2 + ions are in one molecule?

What could you predict about a methane molecule that would most likely be made by using both the quantum model of the atom and John Dalton's model?

What is the molar mass of an unknown hydrocarbon whose density is measured to be 1.97 g/l at stp?

Which is an example of flow of heat through conduction

Which of the following is an extensive physical property of matter? volume viscosity odor density