First, find the volume the solution needs to be diluted to in order to have the desired molarity: You have to use the equation M₁V₁=M₂V₂ when ever dealing with dilutions.
M₁=the starting concentration of the solution (in this case 2.6M) V₁=the starting volume of the solution (in this case 0.035L) M₂=the concentration we want to dilute to (in this case 1.2M) V₂=the volume of solution needed for the dilution (not given)
Explaining the reasoning behind the above equation: MV=moles of solute (in this case KCl) because molarity is the moles of solute per Liter of solution so by multiplying the molarity by the volume you are left with the moles of solute. The moles of solute is a constant since by adding solvent (in this case water) the amount of solute does not change. That means that M₁V₁=moles of solute=M₂V₂ and that relationship will always be true in any dilution.
Solving for the above equation: V₂=M₁V₁/M₂ V₂=(2.6M×0.035L)/1.2M V₂=0.0758 L That means that the solution needs to be diluted to 75.8mL to have a final concentration of 1.2M.
Second, Finding the amount of water needed to be added: Since we know that the volume of the solution was originally 35mL and needed to be diluted to 75.8mL to reach the desired molarity, to find the amount of solvent needed to be added all you do is V₂-V₁ since the difference in the starting volume and final volume is equal to the volume of solvent added. 75.8mL-35mL=40.8mL 40.8mL of water needs to be added
I hope this helps. Let me know if anything is unclear. Good luck on your quiz!
The equation is solved in the manner that the term in the bracket is added first then mutiplication is done as according to Bodmas rule, if an equation contains brackets that need to be solved first then other operation that is division,multiplication, addition and subtraction are performed from left to right .
According to what is known about chemical equilibrium and Le Chatelier's principle, when you increase the amount of the reactants, the reaction will be moved to the products, this is because, the most reactants we have the most products we can produce.
From the given choices, the one that goes according to this reason is the third one: The volume of water vapor increases.
