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How Concentration Affects Reaction

It is a noun in analytical chemistry. The meaning contained in the solution is 1 liter of solute in the molar concentration indicated number.

The physical quantity of the solution composition is expressed by the amount ( molar number ) of the substance contained in the unit volume, and is referred to as the molar concentration of the solute, and is also referred to as the amount concentration of the substance of the solute.

Basic classification

Concentration refers to the amount of a substance in the total amount.

Commonly used concentration representations are:

Percentage by mass (mass fraction, m/m): most commonly used. Refers to the mass of the solute (in grams) per 100 grams of solution.

Percent mass concentration = (solute mass (g)) / solution mass (g)) × 100% = solute mass (g)) / (solute mass (g) + solvent mass (g)) × 100%

Volume percent concentration (volume fraction, V/V): commonly used in alcohol. Refers to the volume of solute (in milliliters) per 100 ml of solution.

Percent volume concentration = (solute volume (mL) / solution volume (mL)) × 100% = solute volume (mL) / (solute volume (mL) + solvent volume (mL)) × 100%

Parts per million (ppm): refers to the mass of solute (in milligrams) contained per kilogram of solution.

Parts per million = mass of solute (mg) / mass of solution (kg)

Mass molar concentration: refers to the amount (in moles) of solute contained per kilogram of solvent.

Mass molar concentration = amount of solute substance (mol) / solvent mass (kg) 1m = 1 mol/kg

Molar fraction: amount of solute (mol) / amount of solution (mol)

Volume molar concentration (molar concentration): The amount of solute (in moles) per liter of solution.

Volume molar concentration = amount of solute (mol) / solution volume (L) 1M = 1 mol / L Formula: c (concentration of the amount of solution substance mol / L) = n (amount of solute substance) / v (solution ml)

Detailed explanation

(1) The amount of solute contained in a unit solution is called the concentration of the solution.

The more solute content, the greater the concentration. The concentration can be calculated by the number of grams of solute, the number of moles or the number of grams equivalents in a given solution. It is generally expressed as a percentage of the weight of the solute contained in the unit solution.

concentration

(2) Degree

Zhu Guangqian, “Philosophical Psychology”, “When we are interested in a kind of art or a natural landscape, the more we appreciate it, the less we feel that we appreciate it.”

Display Method

The symbol is C and the unit is mol/L. The calculation formula is C=n/V. C=1000ρω/M

Concentration refers to the amount of a substance in the total amount.

  1. Quality score (%)
  2. Molar fraction (%)
  3. Amount of substance(mol/L)
  4. Mass molar concentration(mol/kg)
  5. Percentage of mass: Most commonly used.
  6. Volume percent concentration: commonly used in wines.
  7. Volume molar concentration: commonly used in chemistry.
  8. Mass molar concentration

The general concept of concentration refers to the amount of solute in a certain amount of solution or solvent; this general concept of concentration has no clear meaning like the concept of “quantity“; customarily, the volume of solution involved in concentration depends on the volume, the amount of solution The mass is often taken, and the amount of solute is determined by the amount, mass, and volume of the substance.

concentration

It has been stipulated that the narrow concentration is the abbreviation of the concentration of the substance, previously referred to as the molarity, referring to the amount of the substance of the solute B per liter of solution, the symbol is c, the unit is mol/L or mol/dm3, which is:

cB ≡ nB/V

Since the volume of the solution changes with temperature, the concentration of the substance also changes with temperature, under strict heat.

In the calculation of the calculation, in order to avoid the influence of temperature on the data, the molarity of the substance is often not used, and the latter is defined as the amount of the solute substance per 1 kg of solvent, the symbol is m, and the unit is mol/ Kg, ie:

mB ≡ nB /w A =n B /(nA MA)

Wherein B is a solute and A is a solvent. For example, m(NaCl) = 0.1 mol/kg, meaning that 0.1 mol of NaCl is contained per 1 kg of the solution.

The concentration expression that does not change with temperature has a mass fraction in addition to the mass molar concentration, previously referred to as the mass percent concentration, which is the ratio of the mass of the solute to the mass of the solution.

concentration

When the temperature influence is neglected, the mass concentration of the usable substance is used instead of the mass molar concentration. The following is generally used for this approximation.

Finally, it should be mentioned that the concentration of the solution is independent of the amount of the solution. You take one drop from a bottle of 0.1 mol/L NaCl solution, and the concentration of this drop is still 0.1 mol/L.

This seems to be nonsense, but it is not. Because there are two kinds of physical quantities, the first type of physical quantity has additiveness, such as mass, quantity of material, volume, length, etc., such physical quantity is called wide measure, another type of physical quantity does not have additivity, such physical quantity It is called the amount of strength . Concentration is the amount of strength. In addition, pressure (pressure), temperature, density, and the like are also strength amounts.

Blood concentration

Blood concentration refers to the steady-state concentration of the drug in human blood. The steady state concentration means that the daily blood drug concentration of the patient is always relatively constant in the effective range. Each drug takes a certain amount of time to reach a steady state concentration. Antiepileptic drug

It takes about 5 half-lives. The drug half-life refers to the time required for the blood concentration to reach a peak after being taken one time. Based on the half-life of each drug, it can be calculated how long it takes for each drug to perform at its best.

concentration

Such as phenytoin, phenobarbital half-life of 20 hours, then it is necessary to reach a steady state concentration half-life of 20 hours = 100 × 5 hours, that can play the best effect after 5 days; valproate, carbamazepine of The half-life is 10 hours, and it takes 10 hours × 5 half-lives = 50 hours to reach the steady state concentration, that is, 2-3 days to exert the best therapeutic effect.

Some drugs are taken from a small dose and slowly added to an effective amount. Therefore, the time required to reach the steady state concentration in the blood is extended accordingly, and it takes at least 7-10 days to determine whether or not the therapeutic effect is taken when taking these drugs.

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Different patients have certain differences in the absorption, metabolism, and excretion of drugs, especially in children. The same dose of the same weight, some can control the attack cannot, some non-toxic side effects occur some toxic reactions, the same dose, and blood drug concentration is one of the reasons.

Therefore, it is sometimes necessary to determine the blood concentration to achieve the purpose of the individualized medication. The factors affecting the blood concentration of drugs are various, such as heredity, taking other drugs at the same time, liver and kidney gastrointestinal diseases?

Solution concentration

The concentration of the solution can be divided into mass concentration (such as mass percent concentration), volume concentration (such as molar concentration, equivalent concentration)

And three types of mass-volume concentrations.

Percentage of mass

The concentration of the solution is expressed as a percentage by mass of the solute as a percentage of the mass of the entire solution and is expressed by the symbol %. For example, 25% glucose injection refers to 25 grams of glucose in 100 grams of injection.

Percentage by mass (%) = solute mass / solution mass 100%

Volume concentration

(1) The concentration of the molar concentration solution is expressed by the molar number of the solute contained in 1 liter of the solution and is expressed by the symbol mol/L. For example, 1 liter of concentrated sulfuric acid contains 18.4 moles of sulfuric acid, and the concentration is 18.4 mol.

Molar concentration (mol/L) = moles of solute / solution volume (liter)

(2) Equivalent concentration (N)

The concentration of the solution is expressed as the equivalent concentration in terms of the number of gram equivalents of the solute contained in the 1-liter solution and is represented by the symbol N.

For example, 1 liter of concentrated hydrochloric acid contains 12.0 grams of equivalent hydrochloric acid (HCl) at a concentration of 12.0N.

Equivalent concentration = gram equivalents of solute / solution volume (liter)

Mass-volume concentration

The concentration expressed by the mass of the solute contained in the solution per unit volume (1 cubic meter or 1 liter) is called the mass-volume concentration and is expressed by the symbol g/m3 or mg/L. For example, if 1 liter of chromium-containing wastewater contains hexavalent chromium with a mass of 2 mg, the hexavalent chromium concentration is 2 mg/L (mg/L).

Mass-volume concentration = mass of solute (gram or milligram) / volume of solution (m3 or liter)

Conversion formula for concentration units:

  1. Equivalent concentration = 1000.d. mass percent concentration / E
  2. Percentage of mass = equivalent concentration E/1000.d
  3. Molar concentration = 1000.d mass percent concentration / M
  4. Percentage by mass = mass-volume concentration (mg/L)/10.d
  5. Mass-volume concentration (mg/L) = 10 mass percent concentration

5, ppm is the percentage of weight, ppm = mg / kg = mg / L

Namely: 1ppm=1ppm=1000ug/L

1ppb=1ug/L=0.001mg/kg

Where: E – gram equivalent of solute; d – specific gravity of solution, M – molar mass of solute;

Gas concentration

For atmospheric pollutants, common volume concentrations and mass-volume concentrations are used to indicate their levels in the atmosphere.

Volume concentration

The volume concentration is expressed in terms of the volume (cubic centimeters) or (ml/m3) of contaminants per cubic meter of atmosphere. The commonly used expression is ppm, ie 1 ppm = 1 cubic centimeter / cubic meter = 10−6. In addition to ppm, there are also ppb and ppt, the relationship between them is:

1ppm=10−6=one millionth, 1ppb=10−9=one billionth,

1ppt=10−12=one trillion, 1ppm=10 3 ppb=10 6 ppt

Mass-volume concentration

The concentration expressed as the mass of contaminants per cubic meter of the atmosphere is called mass-volume concentration in milligrams per cubic meter or grams per cubic meter.

Its conversion relationship with ppm is:

X=MC/22.4

Concentration

C=22.4X/M

Where: X—the concentration value of the contaminant expressed in milligrams per cubic meter of the meter;

C—the concentration value of the pollutant in ppm;

M—the sub-component of the pollutant.

From the above formula, the following relationship can be obtained:

1ppm=M/22.4(mg/m3) =1000.m/22.4ug/m3

Example 1: Find the ppm concentration of hydrogen fluoride of 30 mg/m3 under standard conditions.

Solution: The molecular weight of hydrogen fluoride is 20, then:

C=30.22.4/20=33.6ppm

Example 2: It is known that the concentration of sulfur dioxide in the atmosphere is 5 ppm, and the concentration value expressed in mg/Nm3 is obtained.

Concentration

Solution: The molecular weight of sulfur dioxide is 64.

X=5.64/22.4mg/m3=14.3mg/m3

Conversion of ppm, ppb and mass content in soil, animals and plants, solid waste:

1ppm=1mg/kg=1000ug/kg

1ppb=1ug/kg=10−3mg/kg

1mg/kg=1ppm=1000ug/kg

1ug/kg=1ppb=10−3ppm

Concentration relationship

Percentage concentration

The volume (ml) of the solute contained in the 100 ml solution, such as 95% ethanol, is 100 ml of the solution containing 95 ml of ethanol and 5 ml of water.

If the concentration is very dilute, it can be expressed in ppm and ppb. 1 ppm = 1 mg ∕ L, 1 ppb = 1 ng ∕ L.

Percentage concentration

The concentration expressed as a percentage of the mass of the solute to the mass of the entire solution is called a mass percentage concentration (abbreviated as a percentage concentration). The mass percentage concentration is a concentration commonly used in daily life and production, and it has no dimension. It will be legally measured in the future

Unit mass fraction (W) is substituted. The mass fraction WB of substance B is the ratio of the mass of the substance B to the mass of the mixture. For example, 5 g of sodium chloride is dissolved in 95 g of water to form a 100 g solution having a mass percentage concentration of 5% and a mass fraction of 0.05 or 5 x 10−2. Medical use 0.9% physiological saline, 0.9% is the mass by volume concentration. It means that 0.9 g of sodium chloride is dissolved in water to form a 100 mL solution.

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Baume (°Bé) is a method of indicating the concentration of a solution. Immerse the Baume hydrometer in the solution to be measured, and the degree obtained is called Baume. Baume is named after the French chemist Antoine Baume. Baume is a pharmacy apprentice and was a professor at the Paris School of Pharmacy. He created a hydrometer – Baume hydrometer.

Baume Hydrometer

There are two types: one is a heavy gauge for measuring liquids heavier than water; the other is a light gauge for measuring liquids that are lighter than water. When the Baume degree is measured, the mass percent concentration of the solution can be conveniently detected from the comparison table of the corresponding chemical handbook.

For example, the Baume degree of concentrated sulfuric acid measured at 15 ° C is 66 ° Bé, and it can be seen that the mass percentage concentration of sulfuric acid is 98%.

Baume Hydrometer

The Baume degree value is large and the reading is convenient. Therefore, Baume degree is commonly used in production to indicate the concentration of the solution (a certain concentration of the solution has a certain density or specific gravity).

The method for determining the Baume degree of different solutions is similar, and the method is used to determine the specific gravity, and the converted concentration is checked according to the measured specific gravity.

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In 2011, the Baume watches of different solutions were used exclusively, such as the alcohol Baume meter and the brine Baume meter. On the Baume watch, there is a concentration of the solution corresponding to the measured solution Baume degree, which can be directly read. No need to look up the table.

Baume degree and specific gravity conversion method

Baume degree = 144.3-(144.3/specific gravity); specific gravity = 144.3/(144.3-pome)

For lighter than water: specific gravity = 144.3 / (144.3 + Baume)

In general, the Baume hydrometer should be measured at a temperature of 15.6 degrees, but the temperature is usually not exactly met when it is actually used, so it needs to be corrected. In general, the temperature difference is 1 degree, and the Baume meter is 0.054 degrees. When the temperature is higher than the standard, the temperature is increased.