A tile cleanser contains 135 g of HCl and 775 g of water. What is the percent by mass of HCl?

1. Mass percentage divides the component mass by the mass of the whole solution. 2. The solution mass is the solute plus the solvent: 135 g + 775 g = 910 g. 3. Form the ratio: 135 g / 910 g = 0.1484. 4. Multiplying by 100 percent gives 14.8 percent HCl. 5. The value 17.4 percent comes from dividing by the water mass of 775 g alone, the classic denominator error. 6. The value 85.2 percent is the water share, which is what is left over. 7. The value 13.5 percent simply reuses the solute digits without dividing at all. _Source: OpenStax Chemistry (CC BY 4.0), Ch 3 "Composition of Substances and Solutions", section 3.4 Other Units for Solution Concentrations_