Reactions in Aqueous Solutions Chapter 4 precipitation reactions

Reactions in Aqueous Solutions Chapter 4 precipitation reactions acid-base reactions redox reactions

Solution Stoichiometry The concentration of a solution is the amount of solute present in a given quantity of solvent or solution. 2

Example 4. 7 How many grams of potassium dichromate (K 2 Cr 2 O 7) are required to prepare a 250 -m. L solution whose concentration is 2. 16 M? Cr=52 K=39 K 2 Cr 2 O 7=39× 2+52× 2+16× 7=294 2. 16 M=? mol/0. 25 L ? =0. 54 mol 0. 54 mol≣ 0. 54× 294=158. 76 g A K 2 Cr 2 O 7 solution.

Example 4. 7 (1)

Example 4. 7 (2)

Example 4. 7 (3)

Example 4. 8 In a biochemical assay, a chemist needs to add 3. 81 g of glucose to a reaction mixture. Calculate the volume in milliliters of a 2. 53 M glucose solution she should use for the addition. n. C 6 H 12 O 6=3. 81/180=0. 021 mol 2. 53 M=0. 021 mol/V L V=0. 0083 L=8. 3 ml

Example 4. 8 (1)

Example 4. 8 (2)

Dilution 稀釋 加溶劑 由濃至稀 Dilution is the procedure for preparing a less concentrated solution from a more concentrated solution. Dilution Add Solvent Moles of solute before dilution (i) Moles of solute after dilution (f) 11 溶液稀釋前後 混合前後溶質的量(重量或莫耳數)不變

Example 4. 9 設取 8. 61 M H 2 SO 4 Y ml 稀釋前n H 2 SO 4=稀釋後n H 2 SO 4

Example 4. 9 (1) Strategy Because the concentration of the final solution is less than that of the original one, this is a dilution process. Keep in mind that in dilution, the concentration of the solution decreases but the number of moles of the solute remains the same.

Example 4. 9 (2)

Example 4. 9 (3)

8 OH- 2 OH- 6 OH- 4 OH- (b) H 3 PO 4 (c) HCl (d) H 2 SO 4

0. 6× 3/2=0. 9 M