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A solution contains 20┬аg of common salt in 280┬аg of water. What is the concentration in terms of mass by mass percentage of the solution?
0.66%
11.1%
66.6%
6.66%
6.66%
To calculate the mass by mass percentage of a solution, we divide the mass of the solute by the total mass of the solution and multiply by 100. In this case, the solute is 20 g of salt and the solvent is 280 g of water, making the total mass of the solution 300 g.
To calculate the mass by mass percentage of a solution, we divide the mass of the solute by the total mass of the solution and multiply by 100. In this case, the solute is 20 g of salt and the solvent is 280 g of water, making the total mass of the solution 300 g.
Think of it like mixing a drink; if you add 20g of sugar syrup to 280g of water, you have 300g of total liquid in your glass. The 'strength' of your sweet drink is the proportion of that sugar relative to the whole glass, not just the water.
\text{Mass % of solution} = \left( \frac{\text{Mass of solute}}{\text{Mass of solute} + \text{Mass of solvent}} \right) \times 100
The formula for mass percentage is determined by the ratio of the component's mass to the entire mixture's mass. By adding 20┬аg┬а(solute)+280┬аg┬а(solvent), we obtain a total solution mass of 300┬аg. Then, we apply the calculation: Concentration=Mass┬аof┬аSolutionMass┬аof┬аSoluteтАЛ├Ч100. Substituting the values gives 30020тАЛ├Ч100=320тАЛ=6.666...% which rounds to 6.66%.
The denominator must always be the total mass of the solution (solute + solvent).
Mass percentage is a unitless concentration expression as it is a ratio of masses (g/g).
Result 6.66% indicates that in every 100g of this solution, there is 6.66g of salt.
Provides a simple, temperature-independent measure of concentration.
Does not account for the chemical identity of the particles (unlike molarity).
Used for labeling consumer products like saline solutions or liquid food ingredients.
Used in industrial processes where mass balance is critical.
Total mass = 20 g + 280 g = 300 g.
Option D is the only mathematically correct result for the given input.
D is correct тАФ The calculation is based on the total mass of the solution, which is 300 g, resulting in 6.66%.
Always verify if the question provides the 'total mass of solution' or the 'mass of solvent' separately; adding them is a common step for full credit.
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