Answer:
He added 992 milimoles of zinc nitrate (Zn(NO3)2)
Step-by-step explanation:
Step 1: Data given
Volume of zinc nitrate = 435.0 mL =0.435 L
Molarity of zinc nitrate = 2.28 M
Step 2: Calculate moles zinc nitrate
Moles = molarity* volume
Moles Zn(NO3)2 = 2.28 M * 0.435 L
Moles Zn(NO3)2 = 0.9918 moles
Step 3: Convert moles to milimoles
Moles Zn(NO3)2 = 0.9918 moles
Moles Zn(NO3)2 = 0.9918 * 10^3 milimoles
Moles Zn(NO3)2 = 991.8 milimoles ≈ 992 milimoles
He added 992 milimoles of zinc nitrate (Zn(NO3)2)