Predict whether the following reaction is still spontaneous at 500
°C N2+ 3H2 -> 2 NH3. Assume AH
= -92.22 KJ/mol and AS= -198. 75
J/K/mol. *​

Adding the numbers 26.45 and 2.55 normally will give an answer of 29. The rule on significant figures on operations involving either subtraction or addition states that the final answer should be rounded to the least number of decimal places among the addends. In the example above, the least number of decimal places is 2. The answer of the addition should be 29.00 which has four significant figures. 

Therefore, the answer is four.