The chemical standard for the quantity of a mole is based on which substance?

Alarge marble is dropped in a graduated cylinder with 35ml of water in it.the water level increases to 49ml.what is the volume of the marble

How do i complete this electrolysis of water lab? i’m at home, so i don’t have the materials, and the lab didn’t properly work and was incomplete at school.

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.