BALANCE AND WEIGHING

Many chemistry experiment involve in different stages. Much time are usually consume during weighing procedures, the main key aspect of time consumer during weighing procedure is weighing to degree of accuracy base on the excessive experimental requirement. Synthetic work, 0.1 or 0.01 gram weighing is satisfactory. But in analytical weighing much work is need on the order of 0.001g or 0.0001g, as such a lot of time is required for weighing process. But wasting of time can be maximized in such a way that weighing is carried out quickly, many experiment cannot be done in the main available times. Also on no condition chemical for weighing should be weighed directly onto the pans of Analytical weighing balance.

Accurate Weighing techniques

There are different method adopted by the scientist when it comes to weighing at such we are going to use Weighing by Difference. To weigh accurate amount of solid to the nearest 0.001g, using bottle weighing is suitable. Below is the procedure;

Place an empty weighing bottle with cap on a weighing balance, determine it weigh and record it on your laboratory report sheet.

Then remove the bottle from the weighing balance and fill the bottle with estimated amount of material to be weigh. Note: if the material are solid shape form, then use mortar and pestle to ground it to powder form. Then wipe and clean the bottle, capped the bottle and weigh it with the content using analytical weighing balance. But if the weigh is significantly different from your expectation, removed the bottle from analytical balance repeat the same procedure and weigh until the required result is obtained. Record you’re your work in your lab notebook.

On the next step, return to working table, turn the solid from the bottle into flask, or any suitable container, at such don’t make any attempt to remove any solid particle stick to the bottle, then re-weigh the bottle after empting it. The lost in the weighing is the exact weigh of solid taken. The method is often use when it is important to weigh exact amount a substance. But when weighing out a substance, example 1.25g of solid, to make specific amount of 0.10M solution, it is a bad practice to use the above method of weighing, in order way round, it is better to use the above method, and finish up with weighing of 1.32g and the solution should be express as follow; (1.32g / 12.6L)M = 0.0105M

The advantage of the above method of weighing practice, is that it help to avoid the method of adding and removing method in order to get accurate desire value and also it help to avoid wasting of chemical, due splash or other process, do to close method of weighing.

APARATUS SET UP

On this topic we are going to explain the process of setting up apparatus, laboratory is field up with many different apparatus, as such before you can become a good scientist, you must be able to handle and use laboratory apparatus properly. It is very important to lubricate the glass when ground glass joints are used, but never lubricate it when high temperature or inert temperature is necessary or when vacuum where involved. On that process, when seized take place on the glasss, the following step should be adhere to facilitate it loosing.

1. Rock the cone in the socket
2. Tap the joint gentle with a block of wood