I need help with question 4,5,6,7 1. What is an indicator? 2. What is a primary

Question

I need help with question 4,5,6,7

1. What is an indicator? 2. What is a primary standard? 3. Why do you need to expel CO2 from the water you are going to use? 4. Write the equations for the neutralizations (acid-base reactions) of (a) NaOHKHP (b) NaOH+HCI . Calculate the amount of 50% NaOH required to prepare 1 L of 0.1 M solution (show calculations) 6. Calculate the amount of conc. HCI required to prepare 0.5 L of 0.1 M solution (show calculations). 7. Calculate the amount of KHP required for a 30 mL titration volume of 0.1 M NaOH (show calculations)

Explanation / Answer

NaOH and KHP reaction

Balanced equation:
NaOH(aq) + KHC8H4O4(aq) ====> KNaC8H4O4(aq) + H2O(l)
Reaction type: double replacement

NaOH and HCl reaction

Balanced equation:
NaOH(aq) + HCl(aq) = NaCl(aq) + H2O(l)
Reaction type: double replacement

50 % NaOH is not mentioned either it is volume by volume or weight by weight.

Molarity of NaOH  

1L of solution, there is 1.53g/ml * 1000mL = 1530g of NaOH solution.

Half of this is NaOH, so 765g

765g has to be converted to mol's by dividing by the molar mass

765g/40g/mol = 19.125 mols in 1L.

Amount of 50% NaOH needed = 1000 x 0.1 / 19.125 = 5.228 ml

Question 6

Concentrated HCl will have 13 M solution.

Amount 13 M HCl required to prepare 0.5L of 0.1M = 500 x 0.1 / 13 = 3.846 ml

Question 7

Moles NaOH reacted with KHP = 30 x 0.1 /1000 =  0.003 Moles

Moles of KHP needed = 0.003 Moles

Mass of KHP needed = 0.003 x 204.22 = 0.61266 gm

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