What is the concentration of acid base solution is concentrated solution

Depending on the specific situation, there is no strict standard for the so-called thick and thin, and it is a customary rule.

Concentrated sulphuric acid is 18mol l (98%)

Concentrated nitric acid is 14mol l (about 68%)

Concentrated hydrochloric acid is 12mol l (about 37%)

Concentrated sodium hydroxide is 12mol l (about 40%)

Concentrated ammonia is 14mol l (about 25%)

If the concentration is less than half of the above, it is "thin"; If the concentration is lower than the above but higher than half of it, there is no strict attribution, and it can be considered dilute and concentrated.

In general, 1 6mol l solution in the laboratory is actually a dilute solution.

1.The preparation of standard liquid has a relatively high accuracy, accurate to four decimal places, while the accuracy of the graduated cylinder is low, only accurate to two decimal places, and the accuracy does not match, so it cannot be measured with a graduated cylinder. However, electronic balances are more accurate and can be matched.

2。The burette is generally an easy-to-clean reagent, which can be washed after many times of washing, and the visual water is evenly distributed without water beads hanging on the wall, and there is no need for reagent testing. The purpose of rinsing is to remove the distilled water in the burette and prevent the standard from being diluted and causing inaccurate titration results.

The Erlenmeyer flask is only used to hold reagents, and there is no need to dry it; It should not be rinsed, because the solution to be tested will remain after rinsing, which will also affect the titration results.

Solution concentration refers to the percentage concentration of the solution. Percentage concentration of solution (concentration can be calculated as the number of grams, gram molecules, or gram equivalent of solutes in a given solution.) ) is the percentage of the weight of the solute contained in a solution (generally a unit solution).

When a soluble substance is dissolved in a solvent, the density of distribution in that solvent is expressed as a percentage, called the percentage concentration of the solution (mass fraction of the solution), which is often expressed as a c% (which can also be expressed as w).

Formula

The formula for calculating the percentage concentration of the solution is:

Mass percentage concentration of the solution Soluble mass The mass of the solution is 100%.

Where, solute mass solvent mass and solution mass.

The above content refers to: Encyclopedia - Percentage Concentration of Solution.

The preparation and concentration comparison of acid-base standard solutions are as follows:

Experimental principle: Hydrochloric acid and sodium hydroxide solution are commonly used as standard solutions in acid-base titration. However, due to the volatile concentrated hydrochloric acid, sodium hydroxide is easy to absorb water and carbon dioxide in the air, and does not meet the conditions of direct preparation, so only the indirect method can be used to prepare hydrochloric acid and sodium hydroxide standard solution

That is, the solution of approximate concentration is first prepared, and then its exact concentration is calibrated with a reference substance.

It is also possible to use the exact concentration of one of the known in the acid-base solution, obtain their volume ratio by titration, and then obtain the accurate concentration of another standard solution according to their volume ratio.

Procedure: Preparation of the solution.

Measure with a clean graduated cylinder, pour it into a clean solution bottle, dilute it with water to 500ml, cover it with a glass stopper, shake it well, and label it with a rental label.

Preparation of solutions.

Weigh NaOH4g with a small beaker on an electronic balance, add water to dissolve, then pour the solution into a clean solution bottle, dilute it with water to 1000ml, cover it with a rubber stopper, shake it well, and label it.

3.Comparison of acid-base standard solution concentrations.

1) Preparation of burettes: Wash two burettes (one acidic and one basic). In the same way that the acid burette is rinsed three times with a small amount of HCl standard solution, the basic burette is also rinsed three times with the NaOH standard solution.

Each time the solution was 5 10ml, and then the HCl and NaOH standard solutions were directly filled with acid-parallel guess burette and alkaline burette respectively.

Remove the air bubbles at the lower end of the piston and rubber tube, adjust the liquid level below the "scale or" scale, and let it stand for 1min before reading, accurate to, and record the reading.

2) Comparison of the concentration of acid-base standard solution: release about 20 30ml of NaOH solution from the alkaline burette into a 250ml clean Erlenmeyer flask, drop 1 2 drops of methyl orange indicator, and then gradually drop the HCl solution into the Erlenmeyer flask from the acid burette, and constantly shake the Erlenmeyer flask to mix the solution.

When the titration is near the end point, a small amount of water can be used to wash the bottle wall, so that the solution attached to the bottle wall can flow down, and continue to titrate drop by drop or half a drop until the solution changes from yellow to orange yellow, that is, the end point of the titration.

If the color observation is in doubt or the endpoint has passed, you can continue to instill a small amount of NaOH solution from the basic burette to make the yellow color reappear, and then titrate with HCl solution until the titration endpoint is orange yellow (and so on until you can judge the titration endpoint more proficiently). The final readings of the two burettes are carefully taken and recorded.

To give you two examples:HCl solution (standard solution that needs to be calibrated);

Add 9 ml of hydrochloric acid (specific gravity) to distilled water and dilute to one liter in a volumetric flask.

Calibration method (acid-base titration).

take 20 ml of sodium carbonate solution (VN2CO3) in a 250 ml Erlenmeyer flask, titrate with this solution, and use methyl orange as an indicator. When the end point is approached, boil to drive away CO2, and after cooling, continue to titrate to the end point (from yellow to orange).Record the volume of consumed HCl vhcl

Calculation: NHCl = NN2CO3 VN2CO3 VHCL.

NaOH solution (standard solution that needs to be calibrated);

Dissolve 4 g of sodium hydroxide in distilled trapped round water and dilute to one liter in a volumetric flask.

Calibration method 1 (titration of HCl).

take 20 ml of HCl solution (VHCL) in a 250 ml Erlenmeyer flask and titrate with this solution, and the indicator is 3 drops of methyl orange. Titration to yellow is the endpoint. Record the volume of VNAOH consumed by NaOH.

Calculation: nnaoh = nhcl vhcl vnaoh.

Calibration method 2 (titration of potassium hydrogen phthalate).

Take 20 ml of potassium hydrogen phthalate solution (actual concentration of N acid) in a 250 ml Erlenmeyer flask, titrate with this solution, and use 2 drops of phenolphthalein as an indicator. Titrate to pale red as the endpoint. Record the volume of VNAOH consumed by NaOH.

Calculation: nnaoh = n acid v acid vnaoh

The pH of a solution is often expressed in pH.

pH value (i.e., hydrogen ion concentration index, hydrogen ion concentration) is a simple value to measure the pH of water, also known as hydrogen ion concentration index and pH value, which is a scale of hydrogen ion activity in solution, that is, a measure of the acidity and alkalinity of the solution in the usual sense. pH has a wide range of uses in medicine, chemistry, and agriculture.

pH describes the strength of the acidity and alkalinity of an aqueous solution, expressed in pH. Under the thermodynamic standard condition, the aqueous solution with pH=7 is neutral, the pH < 7 is acidic, and the pH > 7 is alkaline. The pH range is between 0 14 and is only suitable for dilute solutions, and the pH of solutions with hydrogen ion concentration or hydroxide ion concentration greater than 1mol l is directly expressed by concentration.

pH, also known as hydrogen ion concentration index and pH value, is a scale of hydrogen ion activity in a solution, which is a measure of the acidity and alkalinity of a solution in a general sense.

This concept was proposed in 1909 by the Danish biochemist S Ren Peder Lauritz S Rensen. p stands for German potenz, which means strength or concentration, and h stands for hydrogen ion (H). The ph in Latin is pondus hydrogenii.

Concentrated acid solution dilution method: Slowly inject the concentrated acid solution into water along the wall of the device, and stir continuously with a glass rod to dissipate the heat generated by dilution in time.

Strong alkali solution dilution method: Slowly inject the strong alkali solution into the water along the wall of the device, and stir continuously with a glass rod to make the heat generated by dilution clear in time.

Note: 1. The order cannot be reversed to avoid accidents.

2. Pour acid or alkali into the water, pour slowly along the wall of the vessel, and stir constantly.

Acidic solutions and alkaline solutions are two basic concepts in chemical reactions that are important for many processes in everyday life and industrial manufacturing. In this article, we will take a look at the scope and importance of acidic and alkaline solutions.

Range of acidic solutions.

An acidic solution is a solution whose pH is below 7. They include hydroxides and inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, etc. Acidic solutions have many applications in everyday use, such as disinfection, cleaning, and corrosion protection.

In the laboratory, acidic solutions are also widely used as catalysts and neutralizing reagents for chemical reactions. Acidic solutions are also important for wastewater treatment, as they reduce the alkaline content of the water.

However, acidic solutions also have their undesirable effects. They can corrode metal, damage building materials, and even have an impact on human health.

Range of alkaline solutions.

An alkaline solution is a solution whose pH is higher than 7. The lead group is usually strong alkaline substances such as hydroxides and alkali metal salts, such as sodium hydroxide, potassium hydroxide, etc.

In everyday life, alkaline solutions have many applications, such as detergents, detergents, and fertilizers, among others. In industrial manufacturing, alkaline solutions are also widely used in wastewater treatment, paper production, and metal processing.

While alkaline solutions have many beneficial applications, they can cause adverse effects such as burns, damage**, and eyes. Alkaline solutions can also have adverse effects on the environment, such as contamination of water bodies and soil.

Conclusion Acidic solution and alkaline solution are both important concepts in chemical reactions, which are of great significance to many daily life and industrial manufacturing processes. However, these solutions should be used with caution to avoid their possible adverse effects. When using these solutions, we should always keep safety in mind and ensure the safety and health of ourselves and our surroundings.