What occurs when cr^3+ ions are reduced to cr^2+ ions?

a) electrons are lost and the oxidation number of chromium increases

b) electrons are lost and the oxidation number of chromium decreases

c) electrons are gained and the oxidation number of chromium increases

d) electrons are gained and the oxidation number of chromium decreases

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.

Which statement is true regarding the diagram of circle p? the sum of y and z must be 2x. the sum of y and z must be x. the difference of z and y must be 2x. the difference of z and y must be x

The equation below shows a chemical reaction. a + b + heat —> c + d according to the law of conservation of energy, which statement is true? a. the reactants absorb heat because they have less energy than the products. b. the products release heat because they have more energy than the reactants. c. the reactants generate heat because they have more energy than the products. d. the products require heat to form because they have less energy than the reactants.