How can water have a molarity if theres no diff b/w solute and solvent?

In summary, molarity is the number of moles of a substance per liter of solution. This means that the concentration is not dependent on the type of solvent, as long as it is in a liter of solution. For example, pure water has a molarity of 55.55M, but in a solution of acetic acid, the molarity of water decreases to 52.56M due to the addition of the solute. The mass of one liter of water is 1000g and the number of moles in that mass is 55.55 moles. This calculation is done by dividing the mass by the mass of one mole of water, which is 18.02g.
  • #1
jenzao
48
0
mental block about this please help.
molarity is mols or a substance per Liter of a solution right?
that is, mols of the solute in litres of solution.

1. What is the solution?
2. if its water, then how can you say water has a molarity?
 
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  • #2
Don't think in terms of solution - ie separate solvent and solute. Concentration is just amount per liter, not per liter of water. Thus you have 55.55 moles of water per liter.
 
  • #3
Because molarity is how much stuff you have in a certain amount of volume. It doesn't matter if it is water or an HCl solution.
 
  • #4
So that means that compounds don't necessarily have set molarities right?
for ex, H20 always has mass of 16 + 1 + 1 = 18, and 1 mole is always 18g, but its molarity depends on how many liters of volume 1 mole is contaained in, is that right?

If yes, then why is water said to be 55.5M ??
 
  • #5
jenzao said:
... molarity depends on how many liters of volume 1 mole is contaained in, is that right?

Not quite. Molarity is how many moles are in 1 liter. For water, it happens to be 55.6. 1 liter of water contains 55.6 moles of water.
 
  • #6
To be exact, molarity of pure water is 1000/18.02 = 55.51

However, in the 1M solution of acetic acid there is only 946.9 g of water per liter, so its molarity in such solution will be 846.85/18.02 = 52.56
 
  • #7
Borek said:
To be exact, molarity of pure water is 1000/18.02 = 55.51

However, in the 1M solution of acetic acid there is only 946.9 g of water per liter, so its molarity in such solution will be 846.85/18.02 = 52.56

molarity=no.of moles per volume of soluton in liters
but u did 1000/18.02 how?
 
  • #8
What is mass of 1L of water?

How many moles in that mass?

--
methods
 
  • #9
Let me breakdown:
Re: (1L = 1000 cm^3)
water has an approximate density of 1g/cm^3 (temperature dependent)
Therefore, 1000 cm of pure water has an approximate mass of 1000g
Mass of 1 mole of water = 18.02 g
Hence, no. of moles water in 1000 cm^3 of water = Total mass/mass of 1 mole = 1000 g/18.02g per mole = 55.55 moles
 

1. How can water have a molarity if there's no difference between solute and solvent?

Water can have a molarity because it can act as both a solute and a solvent. In a solution, the substance present in the largest amount is considered the solvent, while the substance present in a smaller amount is the solute. In the case of water, it can dissolve other substances and become the solvent, or it can be dissolved in another substance and become the solute. This is possible because of the unique properties of water, such as its polarity and ability to form hydrogen bonds.

2. Can water have a molarity if it is the only substance present?

Yes, water can still have a molarity even if it is the only substance present. Molarity is a measure of the concentration of a substance in a solution, and it is determined by the amount of solute dissolved in a specific volume of solvent. Since water can act as both a solute and a solvent, it can still have a molarity even if it is the only substance present in the solution.

3. How is molarity different from molality?

Molarity and molality are both measures of concentration, but they are different in terms of the units used. Molarity is expressed in moles of solute per liter of solution (mol/L), while molality is expressed in moles of solute per kilogram of solvent (mol/kg). Additionally, molarity takes into account the volume of the solution, while molality considers the mass of the solvent. Therefore, molarity is affected by changes in volume, while molality is not.

4. How does molarity affect the properties of a solution?

Molarity plays a significant role in determining the properties of a solution. The concentration of a solution can affect its physical and chemical properties, such as boiling point, freezing point, and osmotic pressure. When the molarity of a solution increases, the number of particles in the solution also increases, leading to changes in these properties. For example, increasing the molarity of a solution can cause it to have a higher boiling point and a lower freezing point.

5. What factors can affect the molarity of a solution?

The molarity of a solution can be affected by several factors, such as temperature, pressure, and the amount of solute and solvent present. Changing the temperature or pressure of a solution can alter its volume, which in turn affects the concentration of the solution. Adding or removing solute or solvent can also change the molarity of a solution, as it changes the amount of solute present in a given volume of solvent. Additionally, chemical reactions that occur in a solution can also affect its molarity.

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