Select all the correct answers. Which reactions are single displacement reactions?

2NaBr + CaF2 → 2NaF + CaBr2
SnO2 + 2H2 → Sn + 2H2O
4Na + O2 → 2Na2O
2KClO3 → 2KCl + 3O2
2Al + 6HCl → 2AlCl3 + 3H2

An object becomes electrically charged when: electrons are created in it electrons from it are destroyed electrons are transferred to it protons from it are destroyed protons are created in it

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.

Which of the following is the correct formula for copper (i) sulfate trihydrate? cuso4 · 3h2o cuso4(h2o)3 cu2so4(h2o)3 cu2so4 · 3h2o