The molar mass of i2 is 253.80 g/mol, and the molar mass of ni3 is 394.71 g/mol. how many moles of i2 will form 3.58 g of ni3?

The balanced chemical reaction is this:

3I2 + N2 --> 2NI3

3.58 g NI3 / 394.71 g/mol = 9.07x10^-3 moles NI3

Using the stiochiometric ratio from the reaction,
9.07x10^-3 moles NI3 (3 mol I2 / 2 mol NI3) = 0.0136 mol I2
In grams,
0.0136 mol I2 (253.80 g/mol) = 3.45 g I2

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