Which equation represents a physical change?
(1) h2o(s) + 6.01 kj ==> h2o(l)
(2) 2h2(g) + o2(g) ==> 2h2o(g) + 483.6 kj
(3) h2(g) + i2(g) + 53.0 kj ==> 2hi(g)
(4) n2(g) + 2o2(g) + 66.4 kj ==> 2no2(g)

An alkaline battery produces electrical energy according to the following equation. zn(s) + 2 mno2(s) + h2o(l) zn(oh)2(s) + mn2o3(s) (a) determine the limiting reactant if 17.5 g zn and 31.0 g mno2 are used. (type your answer using the format ch4 for ch4.) (b) determine the mass of zn(oh)2 produced. _ g

An animal cell loses the ability to convert energy stored in food to energy that the cell can use. which of the cell's organelles has stopped working? a.the mitochondria b.the nucleus c.the vacuoles d.the endoplasmic reticulum

Who discovered a pattern to the elements in 1869?