<p>i choose "decrease" on the test and this is my reasoning.</p>
<p>Concentration is measured in terms of the amount of solute dissolved in a given solution.</p>
<p>So say you the solubility of a substance is 60 g in 100g of water. Now you add 20 gram.</p>
<p>Now i calculate concentration in terms of percent solute by mass, which equals grams of dissolved solute divide by grams of solution.</p>
<p>then:
before adding solute: 60 g / 100 g = .6
after: (60g + 20g) / (100g + 20g) = .5</p>
<p>Thereby, the concentration decreases after adding more solute.</p>
<p>First of all, concentration is solute DISSOLVED per amount of solution. The extra solute is not dissolved.</p>
<p>Secondly, why would you add 20g to the 100g of water? You're not adding any extra water, only extra solute.</p>
<p>The extra solute does not dissolve, and the water retains its concentration as a result. Basically, solubility determines the maximum concentration.</p>
<p>Additionally, from a common sense point of view, how would adding more solute (regardless of the situation) decrease concentration? Adding more solvent does that, but the only results of adding solute are an increase in concentration, or no change.</p>
<p>if you add solute to a 'saturated' solution, the concentration will stay the exact same. the extra solute will remain as just that -- solute.</p>
<p>Gold Shadow, you're reasoning on this--</p>
<p>
[quote]
Additionally, from a common sense point of view, how would adding more solute (regardless of the situation) decrease concentration? Adding more solvent does that, but the only results of adding solute are an increase in concentration, or no change.
[/quote]
</p>
<p>that is not necessarily true.
if you have a SUPERsaturated solution, and you add some solute to it, not only will the solute you added stay in solid form, some of the dissolved solute will revert back to precipitate. therefore, you're concentration COULD decrease if you add solute to a supersaturated solution.</p>
<p>"if you have a SUPERsaturated solution, and you add some solute to it, not only will the solute you added stay in solid form, some of the dissolved solute will revert back to precipitate. therefore, you're concentration COULD decrease if you add solute to a supersaturated solution."</p>
<p>Yeah, that's what I was thinking of...</p>