im not sure which one to answer, and i can hardly see the text.
That’s picture right there should help u with your works
The answer is 3.25 x 10 -3 kg is not equal to 325 cg
Answer:
0.136g
Explanation:
A student dissolved 5.00 g of Co(NO3)2 in enough water to make 100. mL of stock solution. He took 4.00 mL of the stock solution and then diluted it with water to give 275. mL of a final solution. How many grams of NO3- ion are there in the final solution?

Initial mole of Co(NO3)2 

Mole of Co(NO3)2 in final solution

Mole of NO3- in final solution = 2 x Mole of Co(NO3)2

Mass of NO3- in final solution is mole x Molar mass of NO3

A. 4 mm.......0.5 mm
B. 1.5 mm......same size