Given the redox reaction in an electrochemical cell:
Ni(s) + Pb2+(aq) + Ni2+(aq) + Pb(s)
A salt bridge is used to connect
A) Ni(s) and Pb(s)
B) Pb2+(aq) and Ni2+(aq)
C) Ni(s) and Ni2+(aq)
D) Pb2+(aq) and Pb(s)

Please help me

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.

7. in the cycle, a virus integrates its dna into the host's dna, and its dna is replicated when the host dna is replicated. a. infectious b. retroviral c. lysogenic d.lytic

Ok, so i have 2 questions. try to answer them both: (the topic is fire) 1) how can you represent the chemical reaction of fire? 2) what kind of bond is formed in this chemical reaction