Flask A Flask B Flask C 25.0 mL of 0.200 M HCN 50. 0 mL of 0.300 M NaCN 10. 0 mL
ID: 589974 • Letter: F
Question
Flask A Flask B Flask C 25.0 mL of 0.200 M HCN 50. 0 mL of 0.300 M NaCN 10. 0 mL of 0.100 M NaOH Based on these flasks, contents, and concentrations, match the following answers to their respective inquiries. How many moles of HCN are in Flask A? A. 0.005 m How many moles of CN are in Flask B? B. 0.015 m When the contents of flasks A and B are combined, what is the resulting concentration of HCN? C.0.0667 M D. 0.20 M When the contents of flasks A and B are combined, what is the resulting concentration of CN?Explanation / Answer
When flask A and B are mixed to form the buffer .
Before mixing [HCN] in flask A = 25x0.2 = 5 mmoles = 0.005 mol
before mixing the moles of NaCN in flask B = 50x0.3 /1000 = 0.015 mol
we have HCN and NaCN in the buffer solution after mixing.
HCN + NaCN
25x0.2/75= 0.067 50x0.3/75=0.2
NOw NaOH 10ml of 0.1 M is added to this
HCN + OH- -----------------> CN- + H2O is the reaction that takes place.
0.067 0 0.2 inital concentrations
The answers are
Q1) moles of HCN in flask A = 0.005
2) moles of NaCn in flask B = 0.015
3) [HCN] after mixing A and B = 0.067 M
4) [CN-] after mixing = 0.2M
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