How to calculate concentration of HCl

Hydrochloric acid, abbreviation HCl(aq), is a common acid both in the body and in the lab. It is, for example, a major component of gastric acid (pH 1-2, 0.5% w/v HCl). In experiments, it is used among other things to set the pH in buffers (e.g. Tris) and to reveal antigens (e.g. BrdU). Chemically speaking, it is a solution of the gas hydrogen chloride = HCl(g) in water.

Conversion % HCl to M HCl

chemical/physical data

• 37% w/w HClaq has a density of 1.19 kg/L [1][2]
• molecular weight of HCl = 36.5 g/mol [3][4]

% to molar conversion

• % w/w HCl to w/v HCl: 37% HCl x 1.19 kg/L density = 0.44 kg/L HCl
• w/v to mol/v: 0.44 kg/L / 36.5 g/mol = 12 mol/L

Thus, fuming/concentrated HCl 37% is 12 molar (= M = mol/L).

diluted HCl from concentrated HCl

• 1M HCl: add 1mol/12M = 83 ml conc. HCl to 1L of water or 8.3ml to 100ml
• 2M HCl: add 2mol/12M = 167 ml conc. HCl to 1L of water or 16.7ml to 100ml

(other calculation start out with 37.5% and arrive at 82ml for 1M HCl [5])

Safety

• Concentrated HCl is a very strong acid that will burn your skin instantly upon contact! Wear gloves, goggles, and lab coat.
• Do not make the mistake of adding water to concentrated HCl. It has to acid into water. If you do it the wrong way the first drops of water mixing with the concentrated acid will heat up, evaporate, and can send drops of acid flying out of the container onto you.
• HClaq above 25% w/w ~ 8M is corrosive and HClaq above 10% ~ 3M is irritant

See also

TITRATION an analytical procedure of determining the concentration of one substance in solution by reacting it with a solution of another substance whose concentration is known, called a standard solution.

Students find that 15.30 milliliters of aqueous sodium hydroxide solution neutralizes 20.00 milliliters of a hydrochloric acid solution. The aqueous sodium hydroxide solution has a concentration of 0.095 moles per liter. What is the unidentified concentration of the aqueous hydrochloric acid solution? Give your answer to three decimal places. (A) 0.073 moles per liter, (B) 0.146 moles per liter, (C) 0.037 moles per liter, (D) 0.938 moles per liter, (E) 0.469 moles per liter.

In this question, we must determine the concentration of an aqueous hydrochloric acid solution from experimental data. First, we need to write a balanced chemical equation for the neutralization reaction of sodium hydroxide with hydrochloric acid.

A neutralization reaction involving strong acids and bases follows the general pattern shown here. So in the balanced chemical equation, hydrochloric acid and sodium hydroxide solutions react to produce aqueous sodium chloride and water. We are told in the problem that 15.30 milliliters of sodium hydroxide base neutralizes 20.00 milliliters of hydrochloric acid. We also know that the concentration of the sodium hydroxide solution is 0.095 moles per liter.

Determining the concentration of the hydrochloric acid solution will involve three steps. First, we need to calculate the number of moles of base that reacted. Then we need to convert moles of base to moles of acid using the molar ratio from the balanced chemical equation. Finally, in step three, we will calculate the molar concentration of the acid.

The units of molar concentration are moles per liter. So before starting step one, we should convert our volume measurements from milliliters to liters. To make the conversion from milliliters to liters, we should divide each measurement by 1000. Let’s take a moment to record these values in our chart.

To calculate the number of moles of sodium hydroxide base, let’s make use of the following equation. Let’s multiply the concentration of the base, which is 0.095 moles per liter, by the volume of the base, which is 0.01530 liters.

Now that we have the number of moles of base, we need to use the molar ratio from the balanced equation to find the number of moles of acid that reacted. The molar ratio of hydrochloric acid to sodium hydroxide in the reaction is one to one. Therefore, the number of moles of acid that reacted is the same as the number of moles of base. For now, let’s wait to round our answer until the last step of the calculation.

Next, let’s use the number of moles of acid and the volume of the acid to calculate the molarity, or molar concentration, of the acid. We should divide the number of moles of acid by the volume in liters of acid. Now that we’ve determined the molar concentration of the hydrochloric acid solution, we must round our answer to three decimal places. The result is 0.073 moles per liter.

In conclusion, the concentration of the aqueous hydrochloric acid solution is 0.073 moles per liter, or answer choice (A).

Let's assume you are titrating a strong acid (10 mL unknown concentration HCl) with a strong base (1.0 M NaOH). It takes 25mL of NaOH to neutralize the acid. If you solve for#M_A#you will see that

#M_A#= (#M_BV_B#) /#V_A#

or#M_A#= (1.0M x 25mL) / 10

#M_A#= 2.5M HCl

This works because M = moles/L

*Note: You do not need to convert volumes of acid and base to liters as long as both are expressed in same unit (mL).

Answer link

Related questions

• How do you calculate concentration from absorbance?

• How do you calculate dilution factor?

• How do you calculate serial dilutions?

• How to calculate concentration of solution when it's diluted?

• What are some examples of dilution calculations?

• What would be the concentration of a solution made by adding 250 mL of water to 45.0 mL of 4.2 M KOH?

  What is the concentration of HCl?

  Hydrochloric acid (HCl) is supplied commercially at concentrations mainly within the range 28–36% w/w. At these concentrations it evolves hydrogen chloride vapour with a sharp irritant odour.

  How is concentration calculated?

  The standard formula is C = m/V, where C is the concentration, m is the mass of the solute dissolved, and V is the total volume of the solution. If you have a small concentration, find the answer in parts per million (ppm) to make it easier to follow.

  What is the concentration of 25% HCl?

  Solution : `25%(w/v)` solution of HCl corresponds to 25g of HCl present in 100 mL of solution. <br> Amount of HCl present in 1000 mL of solution = 250 g <br> `"Molarity"=250/36.5 xx1000/1000 = 6.85" M(GMW of HCl) = 36.5)"` .

  What is the concentration of 20% HCl?

  20.0% (by mass) aqueous solution of HCl suggests the presence of 20.0 g of HCl in 100 g of the solution. So, the mass of water (solvent) present in it is equal to (100-20.0) g or 80.0 g. Hence, 1 kg (or 1000 g) of water contains 6.86 mol of HCl. So, the molality of the solution is 6.86 mol/kg.