Calculate the molecular weight of MgSO4.

First, we need to balance the equation by making sure that the number of atoms on each side of the equation is the same. {eq}Na_2B_4O_7\cdot 10H_2O + H_2SO_4 rightarrow 4H_3BO_3 + Na_2SO_4 + 5H_2O {/eq} Now, let's determine the moles of borax (Na2B4O7 10H2O) using its molar mass: {eq}molar mass of Na_2B_4O_7\cdot 10H_2O = 381.37 g/mol {/eq} {eq}100 lb of borax = 100 lbcdot \frac{453.592 g}{1 lb} = 45,359.2 g {/eq} {eq}moles of Na_2B_4O_7\cdot 10H_2O = \frac{45,359.2 g}{381.37 g/mol} \approx 118.9 moles {/eq} According to the balanced equation, 1 mole of borax reacts with 1 mole of sulfuric acid (H2SO4). Therefore, we need 118.9 moles of sulfuric acid to react completely with the given amount of borax. Now, let's convert moles of sulfuric acid to mass: {eq}mass of H_2SO_4 = moles of H_2SO_4\cdot molar mass of H_2SO_4 {/eq} {eq}molar mass of H_2SO_4 = 98.08 g/mol {/eq} {eq}mass of H_2SO_4 = 118.9 molescdot 98.08 g/mol \approx 11,690.8 g {/eq} Finally, let's convert mass of sulfuric acid to gallons using its specific gravity (sp gr): {eq}specific gravity of H_2SO_4 = 1.83 {/eq} 1 gallon of water weighs \approx imately 8.33 lbs. {eq}11,690.8 gcdotfrac{1 lb}{453.592 g}cdotfrac{1}{8.33 lb/gallon}cdotfrac{1}{1.83} \approx 1,146.6 gallons {/eq} Therefore, \approx imately 1,146.6 gallons of sulfuric acid solution is necessary to react completely with 100 lb of borax to form boric acid.