3. A certain Chemical Industry company has a quality control job opening. The job is open for any major with basic knowledge of chemistry. You decided to apply. In the interview the HR personnel gives you a sealed folder from a certain lot to test your laboratory experience, as well as your quantitative and volumetric analysis skills. The chemical contained in the sample is benzoic acid (C-H602) and it is known to be a monoprotic acid. In order to get the job, you need to determine if the sample's purity is acceptable based on their standards. Inside the folder you found a vial with a solid sample labeled BA-I, a periodic table, and the following data: 1.250 g of the sample required 20.15 mL of 0.500 M concentration of NaOH to reach the end point. The lot can be denied if the purity is below 99.5 % purity. 1) What is the purity in the sample?
2) Is it the purity acceptable?
3) Would you repeat the titration experiment?

1) 97.6%

2) No the purity is not acceptable because the standard is 99.5% purity.

3) Yes I will repeat the titration experiment to confirm my result.

Explanation:

Equation of the reaction;

C7H6O2(aq) + NaOH(aq) > C7H5ONa(aq) + H2O(aq)

From the information provided;

Number of moles of NaOH reacted = concentration × volume = 20.15/1000 × 0.500 = 0.01 moles

From the reaction equation;

1 mole of C7H6O2 reacts with 1 mole of NaOH

Hence 0.01 moles of C7H6O2 will react with 0.01 moles of NaOH

Mass of C7H6O2 reacted = number of moles of C7H6O2 × molar mass of C7H6O2

Molar mass of C7H6O2 = 122.12 g/mol

Mass of C7H6O2 reacted = 0.01 moles × 122.12 g/mol = 1.22 g

Percentage by mass of pure C7H6O2 in the impure sample = 1.22/1.250 × 100 = 97.6 %

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.