b. How many mEq of NaOH must be added in order to adjust the volume and

concentration to 100 mL of 1.0 Eq/L NaOH solution? In order to determine how many

mEq of NaOH must be added you must first ascertain the number of mEq present in the

desired volume and concentration of solution. You desire 100 mL of a 1.0 Eq/L NaOH.

With this information the number of mEq desired can be calculated.

L

1.0 Eq

1000 mEq

100 mL X --------X -------- X ---------- = 100 mEq of NaOH desired

1000 mL

L

Eq

mEq needed = mEq desired -- mEq in flask

100 mEq -- 81 mEq = 19 mEq needed

Thus, 19 mEq of NaOH needs to be added to the flask and sufficient quantity

(q.s.) volume to 100 mL in order to obtain a 1.0 Eq/L NaOH solution.

c. How much stock 10 Eq/L NaOH must be added to the flask in order to adjust

the concentration to 1.0 Eq/L? Multiply the number of mEq needed times the

concentration of the stock along with appropriate conversion factors for the volume and

concentration to obtain the desired results.

Eq

L

1000 mL

19 mEq X ----------X ------X -------- = 1.9 mL

1000 mEq 10 Eq

L

1.9 mL of the stock solution must be added and the solution Q.S. to 100 mL

to yield the desired solution.

MD0837

7-7

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