Answer:
electrons should be added to one of these spheres to make it electrically neutral.
Explanation:
Total charge on each sphere = +3.0 μC =

In order to neutralize the positive charge equal magnitude of negative charge is to be added.
Total charge electrons, Q= -3.0 μC =
Number of electrons = n
Charge on a single electron, e = 
Q = n × e


electrons should be added to one of these spheres to make it electrically neutral.
At the beginning of the war the Northern states had a combined population of 22 million people. The Southern states had a combined population of about 9 million. This disparity was reflected in the size of the armies in the field. The Union forces outnumbered the Confederates roughly two to one.
Also this should be listed for history
Answer: 714 g Al2O3
Explanation: Solution attached
First convert mass of O2 to moles
Do the mole ratio between O2 and Al2O3 from the balanced equation.
Convert moles of Al2O3 to mass using its molar mass.
Atomic number or the number of protons in the element.