3. 3. A 90.-mL sample of juice was titrated with the I2(aq) solution described above using a sb buret. The initial reading of the sb buret was 58.3 mL. When the endpoint was reached, the reading on the sb buret was 26.9 mL. How many mg of Vitamin C were in the juice sample

2765mg of Vitamin C assuming the concentration of I2 = 0.500M

Explanation:

Iodine, I2, reacts with vitamin C in a ratio of 1:1 (The moles of  I2 added = Moles of Vitamin C in the sample). To solve this question we must find the difference in volume from the initial reading to the endpoint reading. Now, ASSUMING the molar concentration of the I2(aq) solution is 0.500M we can find the moles of I2 = Moles of Vitamin C. With its molar mass -176.12g/mol- we can find its mass:

Moles I2:

Volume  = 58.3mL - 26.9mL = 31.4mL = 0.0314L * (0.500mol / L) = 0.0157 moles I2 = Moles Vitamin C

Mass Vitamin C:

0.0157 moles * (176.12g/mol) = 2.765g of Vitamin C * (1000mg/1g) =

2765mg of Vitamin C assuming the concentration of I2 = 0.500M

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.