A chemist needs to create a series of standard Cu2+(aq) solutions for an absorbance experiment. For the first standard, he u pipet to transfer 10.00 mL of a 2.86 M Cu2+(aq) stock solution to a 250.0 mL volumetric flask, and he adds enough wate lilute to the mark. He then uses a second pipet to transfer 25.00 mL of the second solution to a 50.00 mL volumetric flask, and he adds enough water to dilute to the mark. Calculate the concentration of the Cu2+(aq) solution in the 50.00 mL volumetric flask. concentration:

Phenobarbital was introduced in 1912 for the treatment of epilepsy. It is an anti-convulsant and sedative-hypnotic drug and used to control seizures. The measurement of phenobarbital is by fluorescence method. A 5.00 mL aliquots of an unknown containing phenobarbital were delivered to 50.00 mL volumetric flasks. The following volumes of a standard solution of phenobarbital, 2.00ug/mL, were then introduced to the volumetric flasks before diluting to volume with the corresponding signals on a fluorometer equipment. Find the concentration of phenobarbital in the original unknown sample.

A sample with a mass of 1.340 g was dissolved in water, releasing chlorine ions. The aqueous solution was treated with access AgNO3(aq), the AgCl precipitate collected and weighted. Its mass was 2.709 g. What percentage by mass was the original sample? Make sure to use the correct number of significant figures in your answer.

O Chemical Reactions Standardizing a base solution by titration 3/5 Bis A chemistry student needs to standardize a fresh solution of sodium hydroxide. He carefully weighs out 36. mg of oxalic acid (H2C2O4), a diprotic acid that can be purchased inexpensively in high purity, and dissolves it in 250. mL of distilled water. The student then titrates the oxalic acid solution with his sodium hydroxide solution. When the titration reaches the equivalence point, the student finds he has used 35.1 mL of sodium hydroxide solution. Calculate the molarity of the student's sodium hydroxide solution. Round your answer to 2 significant digits. Ом OP G