Common mistakes

A common mistake for beginners in mass spectrometry is to confuse average atomic mass and isotopic mass. For example, the average atomic mass for chlorine is close to 35.45, but this average is of the numbers and masses of Cl and Cl isotopes. This average must be used for instruments that cannot differentiate isotopes (for example, gravimetric balances). Mass spectrometers do differentiate isotopes by mass, so it is important in mass spectrometry that isotopic masses be used... 

The slip velocity between gas and liquid is v, = Vc Vi. For two-phase gas/liqiiid flow, Ri + Rc = 1. A very common mistake in practice is to assume that in situ phase volume fractious are equal to input volume fraclions. 

All areas of the cooling water system where a specific form of damage is likely to be found are described. The corrosion or failure causes and mechanisms are also described. Especially important factors influencing the corrosion process are listed. Detailed descriptions of each failure mode are given, along with many common, and some not-so-common, case histories. Descriptions of closely related and similarly appearing damage mechanisms allow discrimination between failure modes and avoidance of common mistakes and misconceptions. 

A note of caution about roof fasteners. A common mistake is to fix a galvanised or aluminium roof in place with nails or screws of a different metal copper or brass, for instance. The copper acts as cathode, and the zinc or aluminium corrodes away rapidly near to the fastening. A similar sort of goof has been known to occur when copper roofing sheet has been secured with steel nails. As Fig. 24.6 shows, this sort of situation leads to catastrophically rapid corrosion not only because the iron is anodic, but because it is so easy for the electrons generated by the anodic corrosion to get away to the large copper cathode. 

You should be careful not to omit any steps. Care should be taken not to make the job hazards too detailed. Too much detail will make a JHA ineffective. Make sure that only safety steps are recorded. One of the common mistakes is to mix work elements with job hazards. A JHA is not intended to document work process instructions, although some people believe that they should be included. 

Another common mistake often uncovered is electrical equipment w hich is not consistent with the design area classification. See Chapter 17. 

One of the most common mistakes in closing a sale is forgetting to ask for the business. Even sales professionals make this error, sometimes out of a misplaced sense of nicety or a reluctance to appear pushy. In the case of selling PSM, you are asking for senior-level support of an important initiative. You will need this support to be effective and you should not hesitate to request it explicitly. 

This combined manual is designed to help students avoid common mistakes and understand the material better. The solutions manual includes detailed solutions to all odd-numbered exercises in the text, except for the Chemistry Connections exercises. 

It is a common mistake to forget that the ends of lines represent carbon atoms as well. For example, the following molecnle has six carbon atoms (make sure you can count them) ... 

One curved arrow is drawn coming from the alkene and pointing to the proton (take special notice of this arrow, as it is a very common mistake to draw this arrow in the wrong direction). The second curved arrow is drawn coming from the H—Cl bond and pointing to Cl. 

Some fairly common mistakes made in managing electronic SOPs, protocols, and changes to them are listed below. If these can be avoided, the resulting computer system should meet the requirements of the US, Organization for Economic Cooperation and Development (OECD), and Ministry of Health, Labor, and Welfare (MHLW) GLP standards as well as the FDA s Rule on Electronic Record Keeping Electronic Signatures. ... 

Other applications that utilize different types of reversed-phase columns in both dimensions have been advocated by Carr (Stoll et al., 2006) for metabolomics work in small-molecule separations. These stationary phases include a pentafluorophenyl-propyl stationary phase in the first dimension and a carbon-coated zirconia material stationary phase in the second dimension. A common mistake in 2D method development is to mismatch the solvent system the two solvent systems must be miscible as discussed below. 

As a second example, we choose quartz (or any silica polymorph) as a component for a system containing an aqueous fluid and quartz. Now the mole number for the quartz component includes not only the silica in the quartz mineral, the real quartz, but the silica in solution in species such as SiC>2(aq) and IGSiO. Again, the mole numbers of component quartz and real quartz are not the same. A common mistake in geochemical modeling is confusing the components used to describe the composition of a system with the species and phases that are actually present. 

One of the most common mistakes we make during calculations of this kind is forgetting the way k stands for TOOO . Think of it this way a job advertisement offers a salary of 14 k. We would be very upset if, at the end of the first year, we were given just 14 and the employer said he forgot the k in his advert ... 

The style of this latter version is wholly correct and probably more popular than the style we started with. Don t be fooled a common mistake is to look at the table heading and say, we need to multiply K by 10 4 . It has been already ... 

Care It is a common mistake to call the OH- ion a hydroxyl. It is not a hydroxyl is correctly a covalently bound -OH group, for example in an alcohol. 

Pattern 6.4, Refinement Is a Relation, Not a Sequence Do not make the common mistake of thinking that refinement means top-down development it is a fundamental relation between different descriptions regardless of which one was built first. 

It should be kept in mind that there are a number of common mistakes (in both the design and conduct of studies and in how information from studies is used) that have led to unfortunate results, ranging from losses in time and money and the discarding of perfectly good potential products to serious threats to people s health. Such outcomes are indeed the great disasters in product safety assessment, especially since many of them are avoidable if attention is paid to a few basic principles. 

In writing structural isomers as well as any organic compound, remember that carbon forms four bonds One of the most common mistakes that a chemistry student makes is writing an organic structure with a carbon atom having less or more than four bonds. 

Anything personal that steers away from a common mistake. Write about an emotional reaction to an event, a work of art, or another person. 

Avoid the common mistakes admissions committees don t want to see by following the Goof-Proof Rules. 

Another common mistake that interferes with clarity is the use of unclear pronoun references. Pronouns, such as me, you, he, and she, replace nouns. Consider these two cases ... 

The third common mistake with prepositions involves the use of between and among. Between is used when talking about two things. Among is used when talking about more than two things. 

The College Board uses some exams to help train high school teachers so that they can help the next generation of chemistry students to avoid common mistakes. If you check this box, you simply give permission to use your exam in this way. Even if you give permission, no one will ever know it is your exam. 

In any of the gas laws, be sure to express the temperature in kelvin. Failure to do so is a quite common mistake. 

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