Which of the following describes an endothermic reaction?

thermal energy is released by the system.

thermal energy is absorbed by the surroundings.

thermal energy is absorbed by the system.

thermal energy is not transferred.

During endothermic reaction, thermal energy is absorb by the system from the surrounding. The correct option is C.

CuCl2 + 2NaNO3 >  Cu(NO3)2 + 2NaCl

using molar masses:-
Theoretical yields:-
63.54 + 2(35.45) g  of CuCl2  produces  2(22.98 + 35.45) g of NaCl
    134.44  g 116.86 g
       31.0 g 31.0 * 116.86 /134.44=26.95g  
 
 So percentage yield is 21.2* 100 / 26.95    =  78.7%  to nearest tenth