Question 6 Review

Which sample, when dissolved in 1.0 liter of water, produces a solution with the highest boiling point?

A

0.1 mole Ki

B

0.2 mole KI

0.1 mole MgCl2

0.2 mole MgCl2

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0.2 mol MgCl₂

Explanation:

ΔT = Kb . m . i

ΔT = Boiling T° of solution - Boiling T° of pure solvent

Kb is a constant. For water is 0.52 °C/m

m = molality (moles of solute in 1kg of solvent)

i = numbers of ions dissolved.

That's all the elements for the formula to determine the elevation of boiling point.

We assume, that molality will be at least the same for salts with 0.1 moles and 0.2 moles. For 0.1 mol :

1L of water contains 1000g of it, so we can also say that 1kg of water is contained in 1 L of water. Remember that density is 1g/mL or 1kg/L

So concentrations for 0.1 moles are, 0.1 mol/kg and for 0.2moles, 0.2 mol/kg. Let's dissociate the salts to determine i:

KI  → K⁺  +  Cl⁻     i = 2

MgCl₂  → Mg²⁺  +  2Cl⁻    i = 3

The highest difference will be at the 0.2 moles of MgCl₂, so that will be the sample that produces a solution with the highest boiling point.

Boiling T° of solution = 0.52 °C/m . 0.1m . 2  + 100°C = 100.10°C

Boiling T° of solution = 0.52 °C/m . 0.2m . 2  + 100°C = 100.20°C

Boiling T° of solution = 0.52 °C/m . 0.1m . 3  + 100°C = 100.15°C

Boiling T° of solution = 0.52 °C/m . 0.2m . 3  + 100°C = 100.31°C

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !

sure im new too!

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