[chelovek]

In the problem, I'm dealing with an ideal gas and thus have Cv=3R/2. The pressure is 1atm, the system is at constant volume, and I have a temperature change of 100.

Since dE=dQ=CvdT, can Q be calculated correctly just by taking Cv*100?

Furthermore, since this is at constant volume, work would be 0, and ДE=Q, correct?

[Yggdrasil]

Everything you've said is correct, although Cv = (3/2)R applies only for monatomic ideal gasses (for diatomic ideal gasses you have Cv = (5/2)R).