General Chemistry Answers

Animal fats and vegetable oils are triacylglycerols, or triesters, formed from the reaction of glycerol (1, 2, 3-propanetriol) with three long-chain fatty acids. One of the methods used to characterize a fat or an oil is a determination of its saponification number. When treated with boiling aqueous KOH, an ester is saponified into the parent alcohol and fatty acids (as carboxylate ions). The saponification number is the number of milligrams of KOH required to saponify 1.000 g of the fat or oil. In a typical analysis, a 2.085-g sample of butter is added to 25.00 mL of 0.5131 M KOH. After saponification is complete, the excess KOH is back titrated with 10.26 mL of 0.5000 M HCl. What is the saponification number for this sample of butter?

Question1 [21]

1.1 Discuss the four sensory perception of food. (8)

1.2 Identify and describe the chemical basis of five (5) categories of taste. (5)

1.3 Describe four (4) factors that may influence the taste of food, give one example

for each factor. (8)

It is known that 6 g of carbon (C(s)) reacts exactly with 16 g of oxygen gas (O2(g)) producing only carbon dioxide (CO2(g)). If 20 g of coal and 32 g of oxygen gas were mixed, what would be the mass of carbon dioxide produced in the mixture?

Given the reaction: H2SO4 + CaCO3 → CaSO4 + H2O + CO2, and, starting with 2.5 moles of H2SO4, determine the volume occupied by CO2 in the CNTP.

Determine the mass of N2H4 obtained from 140 g of N2, according to the reaction: N2 + 2 H2 → N2H4.

Data: H-1, N-14.

What is the name of the salt formed in the total neutralization reaction between H2S2O3 and Fe(OH)2?

Determine the percentage of copper in cupric sulfate pentahydrate (CuSO4 . 5 H2O)?

Data: H-1, O-16, S-32, Cu-64.

Determine the molecular formula of a substance that has the following proximate formula: 40.9% carbon, 4.5% hydrogen, and 54.6% oxygen. Data: H-1, C-12, O-16.

The concentration of CO2 in air can be determined by an indirect acid–base titration. A sample of the air is bubbled through a solution containing an excess of Ba(OH)2, precipitating BaCO3. The excess Ba(OH)2 is back titrated with HCl. In a typical analysis, a 3.5-L sample of air was bubbled through 50.00 mL of 0.0200 M Ba(OH)2. Back titrating with 0.0316 M HCl requires 38.58 mL to reach the end point. Determine the parts per million of CO2 in the sample of air, given that the density of CO2 at the temperature of the sample is 1.98 g/L.

Animal fats and vegetable oils are triacylglycerols, or triesters, formed from the reaction of glycerol (1, 2, 3-propanetriol) with three long-chain fatty acids. One of the methods used to characterize a fat or an oil is a determination of its saponification number. When treated with boiling aqueous KOH, an ester is saponified into the parent alcohol and fatty acids (as carboxylate ions). The saponification number is the number of milligrams of KOH required to saponify 1.000 g of the fat or oil. In a typical analysis, a 2.085-g sample of butter is added to 25.00 mL of 0.5131 M KOH. After saponification is complete, the excess KOH is back titrated with 10.26 mL of 0.5000 M HCl. What is the saponification number for this sample of butter?