Question

Hi I need help with sig figs with this problem

(0.6216+0.0871)/(0.0740+0.0335)

Answer 1

Actually the problem is this:
Calculate the sodium ion concentration when 74.0 mL of 4.2 M sodium carbonate is added to 33.5 mL of 2.6 M sodium bicarbonate.

My work is:

0.074 g Na2CO3*4.2 mol =0.3108 mol Na2CO3

Na2CO3-->2Na + CO3

2(0.3108) = 0.6216 mol Na+

0.0335L NaHCO3* 2.6mol =0.0871 mol NaHCO3

NaHCO3--> Na + HCO3
1(0.0871 mol NaHCO3)= 0.0871 Na+

M=Total volume of Na/total volume

M=(0.6216 +0.0871)/(0.0740+0.0335)

I got 6.593 but it says I have the sig figs wrong can you please check my work.

Answer 2

Both the 4.2 and 2.6 limit the number of s.f. to 2 so I think your answer should be rounded to 6.6