Instrumental Analysis Exam Questions

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Agrade of "C" or above in a prerequisite course is required for enrollment in an advanced course in chemistry. The chemistry and biochemistry majors are encouraged to take additional courses (e.g. Advanced Organic Chemistry, Inorganic Chemistry, the second semester of Physical Chemistry for biochemistry majors) beyond the required courses specified above.

All chemistry and biochemistry majors must pass a general written comprehensive examination. The examination consists of questions in general chemistry, analytical chemistry, organic chemistry, physical chemistry and biochemistry. All questions on the exam are based upon prior coursework. A study guide and sample questions are available from the department. Students can earn a pass with distinction, pass, low pass or failure. Students normally take the comprehensive exam at the beginning of the spring semester in their senior year.

Instrumental methods of analysis rely on machines. There are several different types of instrumental analysis. Some are suitable for detecting and identifying elementscloseelementA substance made of one type of atom only., while others are better suited to compoundsclosecompoundA substance formed by the chemical union of two or more elements..

The flame emission spectroscopeclosespectroscopeInstrument used to measure properties of light, usually to identify materials. is a scientific instrument based on flame testing. DataclosedataValues, typically letters or numbers. from a spectroscope can be used to:

In the flame emission spectroscope, the coloured light from a vaporisedclosevaporiseTo turn from a liquid to a gas or a vapour. sample can be split to produce an emission spectrumcloseemission spectrumLight given off by a substance, split into its component colours or wavelengths.. The different lines in an emission spectrum look like a coloured barcode. Each metal ion produces a unique emission spectrum.

The metal present in a sample is identified by comparing its spectrumclosespectrumA series of similar waves arranged in order of wavelength or frequency. with reference spectra. These are emission spectra from known metal ions. If two spectra match, they must be from the same metal ion.

A reading is taken from the flame spectroscope for different concentrations of a metal ion in solution. These readings are used to plot a calibration curveclosecalibration curveGraph with the readings from a machine plotted against known amounts of a substance..

Instrumental methods in chemistry can be incredibly useful. Using machines to run experiments offers many advantages to doing them by hand. One such instrumental method is flame emission spectroscopy. This can be used to identify the atoms or ions that are present in a sample using visible light.

Chemical instruments, though not very musical, are fantastically useful. Instrumental methods in chemistry are used to analyse and quantify reactions in a much greater detail then would ever be possible using simple chemical tests or human observations.

Chemical instruments use a range of different techniques to analyse samples with a high degree of precision and accuracy. These techniques range from spectroscopy (the analysis of radiation emitted or absorbed by a sample) to gravimetry (the analysis of a sample by looking at its mass).

By using a computer to handle the data from the chemical instrument, it becomes practical to analyse a great deal more of it. Many chemical instruments will generate thousands of data in a very short space of time, which can be quickly analysed and graphed by a computer. This allows scientists to analyse samples in a much greater detail than they ever could carrying out experiments by hand.

Not only do instrumental methods allow for more data to be generated and analysed, they also allow scientists to carry out many more experiments than they could by hand. Instrumental methods are much less labour intensive than experiments carried out by hand. This means that fewer scientists can carryout more experiments using machines. In addition to being less labour intensive, machines often carry out experiments faster than human beings are able to, and can be set up to run automatically.

Finally, machines are also much more sensitive than a human being. This allows them to use with much smaller samples, ranging down to micrograms of materials. They are also able to observe things on a much smaller scale, such as changes in mass or the order of micrograms, or over times as short as a microsecond.

Flame emission spectroscopy is a common technique to analyse the elements and ions contained within a sample. In flame emission spectroscopy, a sample is placed in a flame, causing it to burn. The light from this flame is then passed through a spectrometer which is able to detect the different wavelengths of radiation that are present. This information is used to produce something called a line spectrum.

The line spectra produced will be unique to the ion or atom contained in the sample. When the sample is placed in the flame it heats up. This causes electrons in the sample to become excited, jumping to higher energy levels. These electrons will then fall back to their original energy levels, releasing radiation as they do so.

This radiation often falls within the visible spectrum an will correspond to specific colours. By analysing these emissions we can produce a line spectrum. These line spectra contain only the light emitted by the sample, and consist of narrow lines found at fixed wavelengths. To illustrate this, the line spectrum for hydrogen is shown below.

Above the line spectrum is shown the visible spectrum of light. We see that the black lines in the visible spectrum correspond to the lines of the emission spectrum. Where these lines appear in the spectrum of a given atom or ion will be determined by its charge and electron configuration.

These unique spectra can be used to determine the identity of single ions and of ions in a mixture. For example, a mixture of hydrogen and sodium atoms would produce the following line spectra.

In reality, this is not one line spectra but two put together, one for hydrogen and one for sodium. If we know which lines should appear in an elements spectrum, we can tease out the individual spectra that make it up:

Line spectra have been incredibly useful in studying the composition of stars and other celestial bodies. By studying the line spectrum of the sun for example, it was possible to discover which elements were present by looking for known spectra in the mixture.

Line spectra can also be used to calculate the concentration of ions in a sample. The intensity of the emission lines in a spectrum will be proportional to the number atoms that are creating it, allowing us to calculate concentrations.

In the pharmaceutical industry, close attention must be paid to drug purity, quality, stability, and safety. Pharmaceutical compounds often have several different structural forms with different molecular shapes. These compounds are also susceptible to thermal degradation, to the pickup and retention of water, and to photodecomposition. One of the best methods to characterize pharmaceuticals from raw product to finished product stage is thermal analysis. The following questions deal with applications of thermal analysis methods to pharmaceuticals.

CHEM 110 Preparation for General Chemistry (3/5) NSc

Introduction to general chemistry with an emphasis on developing problem solving skills. Covers basic concepts of chemistry along with the mathematics required for quantitative problem solving. For students without high school chemistry or with limited mathematics background. Successful completion of CHEM 110 prepares students to enroll in CHEM 142. Prerequisite: assessment of skills by taking the General Chemistry Placement Exam. Offered: AWS.

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CHEM 120 Principles of Chemistry I (5) NSc, RSN

First course in a three-quarter overview of general chemistry, organic chemistry, and biochemistry. Not for students majoring in biochemistry, chemistry, or engineering. Includes matter and energy, chemical nomenclature, chemical reactions, stoichiometry, modern atomic theory, chemical bonding. Laboratory. No more than 6 credits from the following may count toward graduation requirements: CHEM 120, CHEM 142, CHEM 143, CHEM 145. Prerequisite: assessment of skills by taking General Chemistry Placement Exam. Offered: AS.

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CHEM 238 Organic Chemistry (4) NSc

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