What mass of a material with density rho is required to make a hollow spherical shell having inner radius r1 and outer radius r2? (use any variable or symbol stated above as necessary.)'

Select all the correct answers. which changes will increase the rate of reaction during combustion? decreasing the area of contact between the reactants adding more oxygen to the reaction removing heat from the reaction changing the reactants from solid form to powdered form lowering the exposure of the reactants to air