Which of the following chemical equations represents a redox reaction?

a. 2na + 2h2o → 2naoh + h2
b. hcl + koh → kcl + h2o
c. agno3(aq) + nacl(aq) → nano3(aq) + agcl(s) + h2o(l)
d. fe3+ + 3no3– + 3na+ + 3oh–→ fe(oh)3 + 3na+ + 3no3–

Agroup of students is studying convection currents. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other in an area with warm air. after 10 minutes, the balloons are released from a height of 1 meter. which of the following do the students most likely observe? a. the balloons both rise. the cold balloon is larger than the warm balloon. b. the balloons rise at the same rate. both balloons are the same size. c. the warm balloon expands and rises. the cold balloon shrinks and sinks. d. the cold balloon expands and rises. the warm balloon shrinks and sinks.

How many grams of oxygen gas are contained in a 15 l sample at 1.02 atm and 28°c? show your work.

Which of the following shapes would represent a molecule with two bonded atoms and 3 lone pairs on only one of them , trigonal planar , bent , trigonal pyramidal , linear