Metals often form several cations with different charges. cerium, for example, forms ce3+ and ce4+ ions, and thallium forms tl+ and tl3+ ions. cerium and thallium ions react as follows: 2ce4+(aq)+tl+(aq)→2ce3+(aq)+tl3+(aq ) this reaction is very slow and is thought to occur in a single elementary step. the reaction is catalyzed by the addition of mn2+(aq) according to the following mechanism: ce4+(aq)+mn2+(aq)ce4+(aq)+mn3+(aq)m n4+(aq)+tl+(aq)→→ →ce3+(aq)+mn3+(aq)ce3+(aq)+mn4+(aq) mn2+(aq)+tl3+(aq) part a what is the rate law for the uncatalyzed reaction?

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.