Litmus paper, acid-base testing

A solution of a certain salt is tested with litmus paper, and the litmus turns red. What does this tell you about the relative strengths of the acid and base from which the salt is derived ... 

Historically, pH sensitive dyes have been extensively used as indicators in acid-base titrations and in simple spot test papers, even leading to a common phrase in our everyday language, when people or topics are described as having passed the litmus test . The use of complexometric titrations for metal ions was a later but widely... 

POUR 10 ml OF THE SOAP AND DETERGENT SOLUTIONS INTO SEPARATE TEST TUBES. TEST EACH SOLUTION FOR ACID AND BASE WITH LITMUS PAPER AND PHENOLPHTHALEIN. 

Pour the mixture into a tray and test with litmus paper to determine whether it is acidic or basic. (An acid turns blue litmus red a base turns red litmus blue.)... 

Aqueous solutions of most salts test acidic or basic. We can explain this in terms of the strengths of Brpnsted acids and bases. For example, an aqueous solution of sodium acetate tests basic to litmus paper. The solutes are the feeble acid Na and the weak base C2H3O2. Because the base present is a stronger base (not a strong base) than the acid present is an acid, the solution tests basic ... 

JVIake, as in the preceding experiment, dilute solutions of sodium chloride (common salt), potassium nitrate, potassium sulphate, and barium chloride. Test each solution with litmus paper and describe the result. Compare with the action of acids and of bases on litmus paper. 

The pH of solutions may be measured experimentally with an electronic pH meter (highly accurate pH meters can measure to 0.001 pH units) or by using acid base indicators, chemicals that change color in solutions of different pH. A crude but common test for pH involves the use of Hydrion paper strips (litmus paper) that undergo changes similar to those found in indicator solutions. For example, red litmus paper turns blue in a basic solution. 

Red and blue litmus paper is used for testing alkaline and acid solutions. For instance, if we had a solu-tion and wished to know whether it was a base or acid, we would take a piece of red or blue litmus paper and dip it in it. If the red paper turned blue it would indicate a base. If it remained red we would not know whether or not it was neutral or alkaline. Therefore, we would try it with blue litmus paper. If the blue litmus paper would turn red we would then under-... 

USE As acid-base indicator in 0.2% soln in alcohol. pH 4.4 red 6.4 blue. Satisfactory for titrating mineral acids, strong bases, many alkaloids determining alkalinity and temporary hardness in water analysis. Biological stain dye for wool, silk- Not adapted for carbonates, weak inorganic and organic acids, weak bases. Lacmoid is more sensitive than litmus, particularly in form of test paper. 

Directions a) Determine by testing with litmus paper whether solutions of the following salts show a neutral, acidic, or basic reaction sodium chloride, potassium nitrate, sodium sulphate, calcium chloiide, sodium sulphide, copper sulphate, ferric chloride, sodium carbonate, and sodium acetate. (1) Tabulate the results and state in the case of each salt the strength (weak or strong) of the acid and the base from which the salt is derived. 

Chemists operate in the world of quantities that they can see and touch — the macroscopic world of grams, liters, and meters. They Ccirry out chemical reactions by weighing grams of reactants, and they use grams to measure the amount of product formed. They use liters to measure the amount of gas produced. They test a solution with litmus paper to see if it s an acid or a base. 

A fourth property of acids, particularly useful in laboratory tests, is their ability to turn litmus paper red (Figure 13-1). Litmus paper contains a dye that turns red in acid and blue in base. A litmus test simply involves dipping a piece of iitmus paper into a solution to test its acidity. Red litmus indicates acid biue indicates base. 

AgN03(c9) + HiO(/). 4.113 (a) Check with litmus paper, test reactivity with carbonate, or mix with NaOH(c ) and demonstrate neutralization (use an acid-base indicator), (b) Titrate a known quantity of acid with standard NaOH( ) solution, (c) Visually compare the conductivity of an acid solution with that of a sodium chloride solution of the same molarity. 4.115 (a) The complete reaction is Pb (c9) + 2NO3 (09) -1- Na2S04( )... 

Litmus is a substance that is extracted from a type of lichen and absorbed into porous paper. There cire three different types of litmus — red, blue, and neutral. Red litmus is used to test for bases, blue litmus is used to test for acids, and neutral litmus can be used to test for both. Here s how the paper reacts to acids and bases ... 

Litmus paper is a good, quick test for acids and bases. 

Weigh into a flask with a long neck 5 g sodium chlorate and 5 g powdered iodine. Add 40 cm water, shake to dissolve the chlorate and dien add 14 cm cone, nitric acid. Close the mouth of the flask with an inverted beaker. Heat gently with a small flame in the fume cupboard until the iodine has dissolved and then heat the open flask until the chlorine is boiled off, test with a moist blue litmus p r. Pour die contents into a 250 cm beaker. Use 30 cm water to wash die flask and to dilute the solution. Boil the beaker and maintain it on a boiling water bath. Dissolve 5.25 g barium nitrate in 50 cm water and add the solution slowly to the beaker, with continuous stirring. Cool to room temperature. Filter under suction and wash on the filter with small volumes of cold water. Dry by continued suction while pressing between filter paper. Record your yield and calculate the % yield based on Ba. 

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