the answer is 869 mL Na2CO3.
for this problem, the equation is L=mol/M.
first you should perform stoic to convert the grams to moles.
1. divide the 285.06 and 105.99 to get 2.68949...
then you should plug in your values...
1. 2.68949... (you can just use the full number from the previous entry in your calculator)/ 3.13 M
2. you should get 0.859264... LITERS.
3. because the question asks for MILLILITERS, you have to multiply by 1000. (1 L= 1000 mL)
4. check your sigfigs! the minimum number sigfig is 3 places, so the answer is 859 mL Na2CO3!
hope this helped! i’m also learning this, and if it’s wrong then i’m really sorry :(
