Solve a problem

Solutions and concentrationChemistryHigh schoolabout 0:58

3.646 g of HCl is dissolved in water to make 1000 mL of solution. What is the molarity?: animated lesson

A narrated, step-by-step solutions and concentration video lesson with captions. Final answer: M = 0.100005 mol/L.

SpeedLanguage

Video with a synthetic English voice and captions. Pick another language for subtitles in that language, or open the interactive version.

Video narrated by a synthetic voice (Piper TTS, en_US-ljspeech-high voice (LJ Speech dataset, public domain)); the steps come from our maths engine and the answer was checked independently. Download MP4 (0.4 MB) · Captions (WebVTT)

Steps on screen

1. The problem
Worked example
3.646 g of HCl is dissolved in water to make 1000 mL of solution. What is the molarity?
2. Step by step
1. $M(\mathrm{HCl}) = 36.458\ \text{g/mol}$
  Molar mass of HCl
2. $n = \frac{m}{M} = \frac{3.646\ \text{g}}{36.458\ \text{g/mol}} = 0.100005\ \text{mol}$
  Convert grams to moles
3. $V = \frac{1000\ \text{mL}}{1000} = 1\ \text{L}$
  Convert the volume to litres
4. $M = \frac{n}{V} = \frac{0.100005\ \text{mol}}{1\ \text{L}} = 0.100005\ \text{mol/L}$
  Molarity is moles per litre
3. The answer
$\text{M = 0.100005 mol/L}$
M = 0.100005 mol/L
4. Check
- n = MV: 0.100005 × 1 = 0.100005 mol ✓

Transcript

The problem. Here is the problem: 3.646 g of HCl is dissolved in water to make 1000 mL of solution. What is the molarity? Molarity is moles of solute per litre of solution.

Step by step. Molar mass of HCl. Convert grams to moles. Convert the volume to litres. Molarity is moles per litre.

The answer. So the answer is M equals 0.100005 mol/L. Molarity (mol/L, written M) uses the volume of the whole solution, not of the solvent alone. To make a solution, weigh the solute, dissolve it in less solvent, then top up to the final volume.

Check. n equals MV: 0.100005 times 1 equals 0.100005 mol, which checks out.

About solutions and concentration

Molarity, dilution and moles of solute in a solution.

3.646 g of HCl is dissolved in water to make 1000 mL of…