Here's how to calculate the moles of lithium phosphate (Li₃PO₄) in 51 grams:

1. Find the molar mass of lithium phosphate:

* Lithium (Li): 6.941 g/mol

* Phosphorus (P): 30.974 g/mol

* Oxygen (O): 15.999 g/mol

Molar mass of Li₃PO₄ = (3 * 6.941) + 30.974 + (4 * 15.999) = 115.794 g/mol

2. Use the formula: moles = mass / molar mass

* moles = 51 g / 115.794 g/mol

* moles ≈ 0.440 moles

Therefore, there are approximately 0.440 moles of lithium phosphate in 51 grams of the substance.