Weighing rough

It weighs roughly nnc-fifth of Its payload weight. (By comparison, even a small motorcycle weighs more than the rider.)... 

A stone about the size of a softball weighs roughly a kilogram. How many moles of such stones would be needed to account for the entire mass of the Earth, about 6 X 10 grams ... 

Mixture of amines. A suitable mixture for analysis can be prepared by accurately weighing roughly equal amounts of aniline and ethanolamine. The determination is best carried out using a solution made from about 4 g of each amine diluted to 100 mL with acetonitrile in a graduated flask. 

The first sample of X is heated with excess 8N NaOH solution. A dark precipitate forms. This precipitate is dried, ignited in H2 gas, and the metal produced is weighed roughly. Weight—0.5-0.6 grams. 

Twice the desired amount of sample is weighed roughly on a top pan balance (i.e. if a procedure requires a sample weight of 1.5 g, then for duplicate determinations 2X1.5g = 3.0g will be required). 

Weighing and measurements. The rough balances used for macro-scale preparative work are not adequate for senu-micro preparations. For the latter purpose, ordinary analytical balances should... 

It is instructive for the student to construct a rough melting point diagram (compare Section 1,13 and Fig. 1,12, 1) for mixtures of cinnamic acid and urea. Weigh out 1 00 g. each of the two finely powdered components, and divide each into ten approximately equal portions on a sheet of clean, smooth paper. Mix 4 portions of cinnamic acid (A) with 1 portion of urea B) intimately with the aid of a spatula on a glass slide, and determine the melting point (the temperature at which the mixture just becomes completely fluid is noted). Repeat the procedure for 3 parts of A and 2 parts oiB 2 parts of A and 3 parts of B and 1 part of A and 4 parts of B. Tabulate your results as follows —... 

The temperature being constant, a pellet (oT—o 2 gram) of fused naphthalene is caiefully weighed and dropped into the boil-mg-tiibc th.rough the condenser without intenupting the boiling. T hesc pellets are conveniently made in a small bullet-mould. 

For purposes of illustration, consider a lithium crystal weighing one gram, which contains roughly 1023 atoms. Each Li atom has a half-filled 2s atomic orbital (elect conf. Li = ls22s1). When these atomic orbitals combine, they form an equal number, 1023, of molecular orbitals. These orbitals are spread over an energy band covering about 100 kJ/moL It follows that the spacing between adjacent MOs is of the order of... 

For many laboratory operations it is necessary to weigh objects or materials which are far heavier than the upper weight limit of a macro analytical balance, or small amounts of material for which it is not necessary to weigh to the limit of sensitivity of such a balance this type of weighing is often referred to as a rough weighing . A wide range of electronic balances is available for such purposes with characteristics such as, for example,... 

The addition of chemicals to the receptacle must be done outside the balance case. It is good practice to weigh the chosen receptacle on the analytical balance, to transfer it to a rough balance, to add approximately the required amount of the necessary chemical, and then to return the receptacle to the analytical balance for re-weighing, thus giving the exact weight of substance taken. 

Procedure Preparation of 0.05A/ iodine. Dissolve 20 g of iodate-free potassium iodide in 30-40 mL. of water in a glass-stoppered 1 L graduated flask. Weigh out about 12.7 g of resublimed iodine on a watchglass on a rough balance (never on an analytical balance on account of the iodine vapour), and transfer it by means of a small dry funnel into the concentrated potassium iodide solution. Insert the glass stopper into the flask, and shake in the cold until all the iodine has dissolved. Allow the solution to acquire room temperature, and make up to the mark with distilled water. 

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