If 18 lb soda ash are mixed with 75 gal water, what is the slurry concentration when the water volume is increased to 150 gal while keeping 18 lb?

• A. 1.4%
• B. 2.8%
• C. 3.6%
• D. 5.6%

Answer: (A)

Slurry concentration by weight is the mass of solids divided by the total slurry mass (solids plus liquid), expressed as a percentage.

First, find the weight of the water at 150 gallons: 150 gal × 8.34 lb/gal ≈ 1251 lb. Add the solids: 1251 lb + 18 lb = 1269 lb total slurry. The solids fraction is 18 lb / 1269 lb ≈ 0.01417, which is about 1.4%.

Doubling the water while keeping the same solids lowers the concentration roughly by half, from about 2.8% (with 75 gallons) to about 1.4% (with 150 gallons). Thus, the appropriate slurry concentration is approximately 1.4%.