Questions asked by Petya M.

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• For a particular reaction, ΔH = -30.9 kJ and ΔS = -120.8 JK−1. Assume that ΔH and ΔS do not vary with temperature. At what temperature (in Kelvin) will the reaction have ΔG = 0?
  
• If the concentration of a sample was found to be 0.010 mol dm-3 how many moles are there in 150 ml? 1. 1.5 mol 2. 0.15 mol 3. 15 mol 4. 0.0015 mol 5. 0.015 mol
  
• If a 0.489 M solution of L-ascorbic acid is being prepared what mass of solid (in grams) must be added to make a 500 ml of solution?
  
• If 25 ml of 0.667 M solution is diluted to a final volume of 100 ml what is the concentration of the final solution?
  
• If the Ka of ascorbic acid is 7.94 x 10-5 what is the pKa? 1. -4.10 2. 6.10 3. 4.10 4. 4.75
  
• So long as the conical flask is clean why does it not matter if it is wet prior to addition of the 𐑃-ascorbic acid solution? 1. it does matter, it is essential to the experiment that all equipment is clean and dry before use 2. because water does not t
  
• If a 0.489 M solution of L-ascorbic acid is being prepared what mass of solid (in grams) must be added to make a 500 ml of solution?
  
• Which of the following species behave as electrophiles? Select all that apply. CN- CH3CH2+ H+ H2O CHCH
  
• A new enzyme has been discovered in an Antarctic shrimp. This enzyme has been isolated and is being tested for use in the laboratory. At what temperature would you predict the enzyme to show optimal activity?
  
• If a solution is 0.5% (w/v), how many mg/ml is that?
  
• An experiment requires you to add 0.05 ml of solution X and 100 µl of solution Y to 0.85 ml of water. How many and what type(s) of pipette(s) are required?
  
• How many g of sodium carbonate (molecular mass = 106) should be dissolved in 100 ml of water to make a 0.15 M solution?
  
• A stock solution contains 5 g per 100 ml of sucrose. How many ml of this stock solution would you use to prepare 1 litre of sucrose solution at a concentration of 0.25 g per litre?