5) How many grams of NaOH are needed to make 750 mL of a 2.5% (w/v) solution? A)

Question

5) How many grams of NaOH are needed to make 750 mL of a 2.5% (w/v) solution? A) 3.9 g B) 7.5 g C) 19 g D) 20 g E) 50 g 6) Which solution is the least concentrated? Each choice refers to the same solute and solvent. A) 2.4 g solute in 2 mL solution B) 2.4 g solute in 5 mL solution C) 20 g solute in 50 ml. solution D) 30 g solute in 150 mL solution E) 50 g solute in 175 mL, solution 7) What is the molarity of a solution prepared by dissolving 10.0 g of acetone, C3H60, in enough water to make 125 ml of solution? A) 4.65 M B) 1.38 M C) 0.0465 M D) 0.0214 M 8) How many moles of HCI are present in 75.0 mL of a 0.200 M solution? A) 15.0 mol B) 2.67 mol C) 0.375 mol D) 0.275 mol E) 0.0150 mol 9) Calculate the concentration in ppm of a pollutant that has been measured at 450 mg per 150 kg of sample. A) 3.0 ppm B) 6.0 ppm C) 3000 ppm D) 330 ppm E) none of the above 10) What is the conjugate base of HSO4-? A) SO42- B) H2S04 C) H30* D) OH- E) H2SO3

Explanation / Answer

Ans 5 : C) 19 g

(w/v) % = (mass of solute / volume of solution) x 100

2.5 = ( m / 750) x 100

m = 19 g

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