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Encyclopedia > Making up solutions

Contents


Diluting Concentrated Acids

Dilution of concentrated acid should always be done in a fume cupboard.


It is important only to pour acid into water, not the other way around, especially with concentrated acids. Acids may quickly absorb water, creating a lot of heat in the process. When acid is poured into water, the heat can quickly become evenly distributed in the water. If water is poured into acid, the water may quickly boil, spraying acid everywhere.


Hydrochloric acid

Hydrochloric acid can be purchased as either 36% or 32% solution so carefully check the bottle first. The chemical substance hydrochloric acid is the aqueous (water-based) solution of hydrogen chloride (HCl) gas. ...


To make a 1 molar solution (1M):


36%

Add 83.5mL of 36% hydrochloric acid to about 600mL of distilled water in a 1 litre measuring cylinder in a fume cupboard. Make up to 1L, mix well and pour into a labelled bottle. A fume hood, also called a fume cupboard, or colloquially just a hood, is a critical piece of safety equipment in any chemistry laboratory, designed to ensure proper ventilation of hazardous fumes. ...


32%

As above, except use 96mL of hydrochloric acid.


Safety Notes

Concentrated hydrochloric acid is highly corrosive and very irritating to the lungs, wear a face shield and use a fume cupboard. The lungs flank the heart and great vessels in the chest cavity. ...

1M (mole/litre) solutions and above should be labelled IRRITANT.
5M solutions and above should be labelled CORROSIVE.

Nitric Acid

Assuming the concentrated nitric acid is 70%w/v, then to make a 1M solution: The chemical compound nitric acid (HNO3), otherwise known as aqua fortis, is a colorless, corrosive liquid, a toxic acid which can cause severe burns. ...


Add 62mL of concentrated nitric acid to about 700mL of water then dilute to 1L.


Add slowly, stirring constantly with a polypropylene or glass stirring rod. If the solution gets too hot, stop and let it cool down.

0.1M (mole/litre) solutions and above should be labelled IRRITANT.
1M solutions and above should be labelled CORROSIVE.

Sulphuric acid

Concentrated sulphuric acid is highly CORROSIVE and a dehydrating agent. It causes severe burns. It should only be handled under close supervision by an experienced person. Wear gloves and protect the eyes with safety goggles or even better, a face shield. Sulfuric acid (British English: sulphuric acid), H2SO4, is a strong mineral acid. ... Dehydration is the removal of water (hydor in ancient Greek) from an object. ... Watersport goggles Blowtorching goggles and safety helmet Goggles are a form of protective eyewear that usually enclose the eye area to prevent particulates or chemicals from striking the eyes. ...


Add 54mL of concentrated sulphuric acid to about 700mL of iced water and dilute to 1 litre. This is a 1M solution.

1M (mole/litre) solutions and above should be labelled IRRITANT.
4M solutions and above should be labelled 'CORROSIVE.

Ethanoic acid

Known also as acetic acid. The concentrated acid is called Glacial acetic acid as it freezes at 17°C. Glacial acetic acid is CORROSIVE and the vapour is an extreme IRRITANT. Wear gloves and protect the eyes with safety goggles or even better a face shield. Work in a fume cupboard. The chemical compound acetic acid (from the Latin word acetum, meaning vinegar), systematically called ethanoic acid, is the acid that gives vinegar its sour taste and very pungent smell when at high concentrations. ... Watersport goggles Blowtorching goggles and safety helmet Goggles are a form of protective eyewear that usually enclose the eye area to prevent particulates or chemicals from striking the eyes. ... A fume hood, also called a fume cupboard, or colloquially just a hood, is a critical piece of safety equipment in any chemistry laboratory, designed to ensure proper ventilation of hazardous fumes. ...


To make a 1M (mole/litre) solution, add 57mL of the concentrate to about 600mL of distilled water and dilute to 1 litre.

1M (mole/litre) solutions and above should be labelled IRRITANT
4M solutions and above should also be labelled CORROSIVE

Concentrations

Molar solution is used when referring to the molarity of a solution, which expresses its concentration. ...

Help! It won't dissolve

Some substances do not dissolve very readily in water and require special methods.

This dissolves very slowly in water. The best thing to do is to start making it up the day before you need it. Mix the powder into agitated water, then put into the fridge overnight. When you come back in the morning it will have dissolved. The chemical compound sodium alginate is the sodium salt of alginic acid. ...

In general, starch is insoluble in water, but some types of starch e.g. corn starch will dissolve in water provided they are made into a paste first with cold water then dissolved in boiling water. Starch is a complex carbohydrate which is insoluble in water. ... Products made out of cornstarch Cornstarch is the starch of the maize grain, commonly known as corn. ...

Most iron (III) salts do not form stable aqueous solutions. In order to get them to dissolve you need to add a small amount of acid. Add hydrochloric acid to the chloride etc... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... For other meanings of the word salt see table salt or salt (disambiguation). ... Drinking water This article focuses on water as we experience it every day. ...


Reagents used for testing foodstuffs

Biuret reagent The Biuret Reagent is made of sodium hydroxide and copper sulfate. ...


This is used to test for the presence of protein. There are two recipes the first consists of two reagents Biuret A and Biuret B. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...

For the second (Quantitative) recipe, in about 600mL of distilled water, dissolve in order 3g of copper (II) sulfate · 5H2O, 5g of potassium iodide, 9g of potassium sodium tartrate.4H2O, and 8g of sodium hydroxide. Make the dissolved solids to 1 litre. Label the solution IRRITANT Sodium hydroxide (NaOH), also known as caustic soda or lye, is a caustic metallic base used in industry (mostly as a strong chemical base) in the manufacture of paper, textiles, and detergents. ... The chemical compound potassium hydroxide, (KOH) sometimes known as caustic potash, potassa, potash lye, and potassium hydrate, is a metallic base. ... Copper (II) sulfate (CuSO4) is the most common copper salt, made by the action of sulfuric acid on the base copper oxide. ... Copper (II) sulfate (CuSO4) is the most common copper salt, made by the action of sulfuric acid on the base copper oxide. ... Potassium iodide is a white crystalline salt with chemical formula KI, used in photography and radiation treatment. ... Potassium sodium tartrate is a double salt first prepared (in about 1675) by an apothecary, Pierre Seignette, of La Rochelle, France. ... Sodium hydroxide (NaOH), also known as caustic soda or lye, is a caustic metallic base used in industry (mostly as a strong chemical base) in the manufacture of paper, textiles, and detergents. ...


Benedict's reagent is used to test for reducing sugars. It has two recipes. Benedict's qualitative and Benedict's quantitative. Benedicts reagent (also called Benedicts solution or Benedicts Test) is a reagent used as a test for the presence of reducing sugars (such as glucose, lactose, and fructose, but not sucrose) in a solution. ... A reducing agent is a substance used in electrochemistry that reduces another substance. ...


Benedict's Qualitative Reagent

The reagent is made up by first dissolving 173g of sodium citrate and 100g of anhydrous sodium carbonate in about 600ml of distilled water. Then 17.3g copper (II) sulfate · 5H2O is dissolved in about 100ml of distilled water. The two solutions are then mixed together and when cool are made up to 1L with distilled water. Sodium citrate is the sodium salt of citric acid with the chemical formula of Na3C6H5O7. ... Liquids and solids (powders) are anhydrous if they are without water, i. ... Sodium carbonate or soda ash, Na2CO3, is a sodium salt of carbonic acid. ... Copper (II) sulfate (CuSO4) is the most common copper salt, made by the action of sulfuric acid on the base copper oxide. ...


Benedict's Quantitative Reagent

In about 600ml of hot water dissolve

  • 200g of sodium citrate
  • 75g sodium carbonate
  • 125g potassium thiocyanate

In about 100ml of water dissolve

  • 18g of copper (II) sulfate · 5H2O

When the solutions have cooled, mix them together stirring constantly. Add

Potassium ferrocyanide (K4Fe(CN)6·3H2O), also known as yellow prussiate of potash, is a coordination compound forming lemon-yellow monoclinic crystals at room temperature and decomposing at its boiling point. ...

Iodine Solution

  • Iodine solution is used to test for starch.

Recipes vary but 1g of iodine plus 1g of potassium iodide in 100mL water is suitable. Dissolve the iodide then the iodine. Starch is a complex carbohydrate which is insoluble in water. ... Potassium iodide is a white crystalline salt with chemical formula KI, used in photography and radiation treatment. ...


Buffer Solutions

Buffer solutions help to keep the pH of a sample constant. Make up 0.1M citric Acid and 0.2M phosphate solutions then mix as follows, Buffer solutions are solutions which resist change in pH upon addition of small amounts of acid or base. ...

Citric Acid-Phosphate buffers
pH 0.2M Na2HPO4 /ml 0.1M Citric Acid /ml
3.0 20.55 79.45
4.0 38.55 61.45
5.0 51.50 48.50
6.0 63.15 36.85
7.0 82.35 17.65
8.0 97.25 2.75

  Results from FactBites:
 
eNAMEL Online Newsletter: John Burgess - chemical solutions (1170 words)
When making up solutions from solids, or diluting liquids using some instructions, there is not often any information upon the best ways of doing the job, and I propose here to suggest safe, simple and easy methods of going about it.
Make sure the measuring jug to hold the diluted liquid holds at least a litre, and is very clean ; it doesn't have to be dry.
Making up solutions is neither difficult nor inherently dangerous; just proceed slowly, think a little ahead, and read all the instructions and precautions on the bottles.
  More results at FactBites »

 
 

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