If the Chinese hadn't invented gunpowder when they had, how would they fair against the mongols?
Well, the Chinese were conquered by the Mongols. I guess gunpowder here is irrelevant. I mean China would be conquered with or without gunpowder.
I am not sure that without gunpowder the Mongol conquest would have been slower and harder. The Chinese would have spent their resources on other weapons like warhorses, crossbows, fortifications, armor, whatever.
You see at that period gunpowder did not give a serious advantage. We know now that using gunpowder was moving in the right direction. That's why we pay so much intention to it.
And the Song were
very inventive and enthusiastic doing so.
I am of the opinion that if the Mongol invasion had happened a century later the Song would have developed their gunpowder weapons on a
much higher level. The Song would have become the first real gunpowder Empire and they might fight off the Mongols.
Or inventing the gunpowder a couple centuries earlier by the Chinese might have done the same trick.