Which of the following is a redox reaction? A. CuO + H2SO4 → CuSO4 + H2O
B. 3MnO2 + 4A1 3Mn + 2A120,
C. MgCO, → MgO + CO2
D. Mg(OH)2 + 2HCl → MgCl2 +H20

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.

When the ionic compound nabr dissolves in water, br– ions are pulled into solution by the attraction between what two particles? a. the na+ and br– ions b. the na+ ion and the negative end of a water molecule c. the br– ion and the positive end of a water molecule d. the br– ion and the negative end of a water molecule

Which of the following statements best explains why chemistry is testable a) it can measure data by experiments b) it cannot add new evidence c) it cannot be verified d) it is biased