Electrons

Together, the number of protons and the number of neutrons determine an element’s mass number: mass number = protons + neutrons. If you want to calculate how many neutrons an atom has, you can simply subtract the number of protons, or atomic number, from the mass number.

Atomic mass is significant in calculating percentage yield as by using atomic mass of an element is mass of 1 mole of atom. To calculate the theoretical percentage of an element in a compound, we divide the molar mass of element by mass of compound and multiply it by 100.

According to the 1996 edition of Vogel’s Textbook , yields close to 100% are called quantitative, yields above 90% are called excellent, yields above 80% are very good, yields above 70% are good, yields above 50% are fair, and yields below 40% are called poor.

Generally, yield is calculated by dividing the dividends or interest received on a set period of time by either the amount originally invested or by its current price: For a bond investor, the calculation is similar.

Theoretical yield is what you calculate the yield will be using the balanced chemical reaction. Actual yield is what you actually get in a chemical reaction.

This percent yield is just a concept to measure the extent of a chemical reaction because in actual situations, reactions are rarely proceeding to completion. Thus, to put it simply, a chemical reaction can never have 110% actual yield, or anything beyond 100% for that matter.

The percent yield is the ratio of the actual yield to the theoretical yield, expressed as a percentage. However, percent yields greater than 100% are possible if the measured product of the reaction contains impurities that cause its mass to be greater than it actually would be if the product was pure.

An actual yield is the mass of a product actually obtained from the reaction. It is usually less than the theoretical yield.

Usually, percent yield is lower than 100% because the actual yield is often less than the theoretical value. Reasons for this can include incomplete or competing reactions and loss of sample during recovery.

Percent yields can be higher or lower than 100%. A higher percent yield might signal that your product is being contaminated by water, excess reactant, or another substances. A lower percent yield might signal that you mis-measured a reactant or spilled a portion of your product.

How to Improve Your Yield

1. Flame dry or oven dry flask and stirbar.
2. Use clean glassware.
3. Calculate and weigh reagent amounts accurately.
4. Purify reagents and solvents, if necessary.
5. Be sure your reactant is pure.
6. Rinse (3 times with reaction solvent) flasks and syringes used to transfer reactant and reagents.

Percent yield is a calculation that compares how much product we actually produce with how much product that we calculate that we should produce. If we calculate a percent yield of 50%, then it means that we actually produced half of the amount of product that we calculate that we should produce.

The yield and rate of a chemical reaction depend on conditions such as temperature and pressure. In industry, chemical engineers design processes that maximise the yield and the rate at which the product is produced. They also aim to reduce waste and energy costs at all stages of the process.

Catalysts increase the rate of reaction without affecting the yield.

Catalysts only affect the rate of reaction – they do not affect the yield of the reaction. A catalysed reaction produces the same amount of product as an uncatalysed reaction but it produces the product at a faster rate.

The most important catalysts in the human body are enzymes. An enzyme is a catalyst composed of protein or ribonucleic acid (RNA), both of which will be discussed later in this chapter. Like all catalysts, enzymes work by lowering the level of energy that needs to be invested in a chemical reaction.

Catalyst, in chemistry, any substance that increases the rate of a reaction without itself being consumed….Catalyst.

Biological catalysts are called enzymes. There is, for instance, an enzyme in our saliva which converts starch to a simple sugar, which is used by the cell to produce energy, and another enzyme which degrades the excess lactic acid produced when we overexert ourselves.

The name of most enzymes end with “ase”. For example, a phosphatase is an enzyme that removes a phosphate group from a protein. …

Enzymes and catalysts both affect the rate of a reaction. In fact, all known enzymes are catalysts, but not all catalysts are enzymes. The difference between catalysts and enzymes is that enzymes are largely organic in nature and are bio-catalysts, while non-enzymatic catalysts can be inorganic compounds.

Different enzymes that catalyze the same chemical reaction are called isozymes. The International Union of Biochemistry and Molecular Biology have developed a nomenclature for enzymes, the EC numbers (for “Enzyme Commission”).

Temperature: Raising temperature generally speeds up a reaction, and lowering temperature slows down a reaction. However, extreme high temperatures can cause an enzyme to lose its shape (denature) and stop working. pH: Each enzyme has an optimum pH range. Changing the pH outside of this range will slow enzyme activity.

catalyst

• adjuvant.
• agitator.
• enzyme.
• goad.
• impetus.
• impulse.
• incendiary.
• incentive.