1. Describe how you would make 400.0 mL of a 0.0500M solution of NaOH from pure
ID: 1042260 • Letter: 1
Question
1. Describe how you would make 400.0 mL of a 0.0500M solution of NaOH from pure NaOH crystals. Show the calculations needed, and describe how you would make the solution. 2. Calculate the number of moles contained in 0.476g of potassium hydrogen phthalate also known as KHP (remember: KHP, is an abbreviation, not a formula). Show ALL work and include units! 3. A volume of 39.40 mL of 0.0500 M NaOH was needed to neutralize the citric acid in 10.00 mL of 7-Up. Calculate the molarity of citric acid in the 7-Up. Show ALL work! (Hint: Use the balanced equation!)Explanation / Answer
1) volume of solution = 400mL = 0.400L
molarity of solution = 0.05 00M
molar mass of NaOH = 40 g/mol
We know from definition of molarity
molarity = number of moles /volume in L
= ( mass/ molar mass) /V(L)
substituing the known values
0.0500 = (mass/ 40g/mol) /0.4
Thus mass of NaOH to be taken = 0.8 g
Procedure:
weigh exactly 0.8 g of pure NaOH , transfer the whole contents into a 400mL volumetric flask through a funnel, wash the funnel with water and dissolve NaOH in small qantity of water, then make up the solution to the mark to make 400mL of solution.
Q2) number of moles of a substance = mass of substance / molar mass
molar mass of KHP = 204.22g/mol
given mass of sample =0.476g
Thus number of moles of KHP in the sample = 0.476g/ 204.22 g/mol
= 0.00233mol
=2.33x10-3 mol
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