Enthalpy change
When using the formula: q= m x c x change in T, I'm slightly confused about the mass.
If you add 2g of a solid, which dissolves in a 40cm3 solution, would you say the mass is 40g or 42g?
If you add 2g of a solid, which dissolves in a 40cm3 solution, would you say the mass is 40g or 42g?
You always use the mass of the water. So in your example - 40g.
Original post by BigBangTheorist
When using the formula: q= m x c x change in T, I'm slightly confused about the mass.
If you add 2g of a solid, which dissolves in a 40cm3 solution, would you say the mass is 40g or 42g?
If you add 2g of a solid, which dissolves in a 40cm3 solution, would you say the mass is 40g or 42g?
Which exam board?
Original post by haemo
There are two rules:
You use the volume of solution as the mass
If given two or more solutions, the mass is the sum of these volumes
For example, 2g of a solid was dissolved in 40 cm3 of a solution means that the mass is 40.
5g of a solid was dissolved in 50 cm3 of a solution and 30 cm3 of another solution means that the mass is 50 + 30 = 80
You use the volume of solution as the mass
If given two or more solutions, the mass is the sum of these volumes
For example, 2g of a solid was dissolved in 40 cm3 of a solution means that the mass is 40.
5g of a solid was dissolved in 50 cm3 of a solution and 30 cm3 of another solution means that the mass is 50 + 30 = 80
Thanks for the help!
Original post by haemo
There are two rules:
You use the volume of solution as the mass
If given two or more solutions, the mass is the sum of these volumes
For example, 2g of a solid was dissolved in 40 cm3 of a solution means that the mass is 40.
5g of a solid was dissolved in 50 cm3 of a solution and 30 cm3 of another solution means that the mass is 50 + 30 = 80
You use the volume of solution as the mass
If given two or more solutions, the mass is the sum of these volumes
For example, 2g of a solid was dissolved in 40 cm3 of a solution means that the mass is 40.
5g of a solid was dissolved in 50 cm3 of a solution and 30 cm3 of another solution means that the mass is 50 + 30 = 80
If you are using an Hess' cycle and the reactant has two moles, while the product has one mole, how do you work out the enthalpy change for the reactant?
I'm guessing that you would carry out experiments to determine the enthalpy change for each reaction and divide the enthalpy change on the right by two before substracting it from the one on the left. Is that right?
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