I COULDN"T FIND THIS ANSWER ANYWHERE PLZZZ

Cucl2 + 2nano3 cu(no3)2 + 2nacl what is the percent yield of nacl if 31.0 g of cucl2 reacts with excess nano3 to produce 21.2 g of nacl? 49.7% 58.4% 63.6% 78.7%

How many atoms are there in 5.70 mol of mg

Can someone me with 6 to 10 plz this is for masteries test.