Answer:
First, we need to calculate the amount of salt in the 300 mL NaCl solution:
3.0 g/L x 0.3 L = 0.9 g
Next, we need to calculate the amount of salt in the 500 mL 7% NaCl solution:
7 g/100 mL x 0.5 L = 3.5 g
The total amount of salt in the final solution is:
0.9 g + 3.5 g = 4.4 g
The total volume of the final solution is:
300 mL + 500 mL = 800 mL = 0.8 L
Therefore, the final concentration of salt in the solution is:
4.4 g / 0.8 L = 5.5 g/L
The answer is not given among the choices provided.