Mg+2HCl=MgCl2+H2 How many grams of Mg is needed to produce 112 liters of H2 at STP?

Which of the following is an example of physical change not a chemical change? a) a log gives off heat and light as it burns. b) a tree stores energy from the sun in its fruit. c) a penny lost in the grass slowly changes color. d) a water pipe freezes and cracks on a cold night.

Which element has the lowest electronegativity? calcium(ca) gallium(ga) selenium(se) bromine(br)

Which description best characterizes the motion of particles in a solid?