It was Mohnen who capped the Group B win with a lay-up followed by two free throws, as it finished 54-48.
Germany are off to a 1-0 start after having a day off yesterday, while the Americans drop to 1-1.
Hosts Great Britain were left with a problem after slumping to a 51-24 Group A defeat to Australia that left their coach Garry Peel furious.
Australia, bronze medallists in 2008, dominated the game in every department as Britain shot just 21 per cent from the field and failed to make any real impression.
'They know what's coming,' Peel said of his planned post-game team-talk. 'They know that's not the way we play.'
It was a big improvement for Australia, however, after they were made to battle to a 52-50 win over Brazil yesterday.
There was less drama on the men's side, where the USA recovered from yesterday's shock loss to Turkey by beating Italy 77-51 behind 24 points from Jason Nelms and 22 from Nate Hinze.
Also in Group A, Spain improved to 2-0 with a 74-50 win over South Africa, with Alejandro Zarzuela Beltran scoring 24 and Ismael Garcia Moreno 22.
In Group B, Mateusz Filipski had 24 points to lead Poland to a 78-53 win over Japan, while Sebastian Wolk and Dirk Passiwan teamed up to lead Germany to win number two, beating Colombia 59-46.
In the later games, Great Britain's men saw their record fall to 0-2 with a 70-54 loss to Canada, with Patrick Anderson turning in a virtuoso performance for the Canadians.
The veteran, who retired after the Beijing 2008 Paralympics only to return in 2011, showed he still has more than enough to offer as he scored 29 points while collecting 14 rebounds and 10 assists for the first international triple-double of an already distinguished career
Australia beat Turkey 71-64 while in the women's evening games Netherlands beat Canada 70-59 while China were emphatic 72-34 victors over France.