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Flashcards in Energy Changes Deck (67)
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1

How do you find the mass of a solution?

Volume x density (assume density is 1 unless told otherwise)

2

What is the specific heat capacity

The amount of energy that is needed to raise the temperature of a solution by 1 degree

3

What is the specific heat capacity of water?

4.2 J/g/•C

4

When do you not add the masses together and when do you?

Don't add the mass of a solid reactant to the mass of the solution, but if two solutions then add them together

5

What is the equation for molar enthalpy change?

Molar enthalpy change (kJmol-1) = - heat energy transferred / no. of moles

Delta H (triangle H) = -Q / n

6

Equation to find energy change

Energy change (J) = mass of solution (g) x specific heat capacity (J/g/•C) x temp change

Q= m x c x Delta T

7

How does temperature, energy, and molar enthalpy change in an exothermic reaction

Temperature increases
Heat energy transferred is positive
Molar enthalpy change is negative

8

How does temperature, energy, and molar enthalpy change in an endothermic reaction

Temperature decreases, heat energy is negative, molar enthalpy is positive

9

What are exothermic reactions and what is the energy of their products like in relation to the reactants

Exothermic reactions release energy into their surroundings
Products have a lower energy than the reactants

10

What are endothermic reactions and what are their products like in relation to their reactants

Endothermic reactions absorb energy from their surroundings
Products have a higher energy than the reactants

11

Example of an exothermic reaction

N2 + 3H2 = 2NH3 (Haber process)

12

Example of an endothermic reaction

H2 + I2 = 2HI

13

KNOW HOW TO DRAW ENERGY CHANGE DIAGRAMS

🐥🐥🐥

14

What is the bond energy

Bond energy is the energy required to break one mole of covalent bonds.

15

Equation for molar enthalpy change from bond energies

Molar enthalpy change = Sum of bonds broken - sum of bonds made

16

What happens when bonds are broken

It requires energy and is an endothermic process

17

What happens when bonds are made

Energy is produced, it's an exothermic process

18

What is the relative atomic mass (Ar)

The weighted average sum of all the isotopes of an element

19

Equation for relative atomic mass

Ar = sum (isotope mass x abundance) / 100

20

Equation for Mr

Sum of Ar

21

Equation for moles

Mass / Mr

22

What is Avogadro's Law

Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. This means that one mole of any gas will occupy the same volume at the same temperature and pressure.

23

What is the "molar volume" of one mole of any gas?

24dm3 (24000cm3)

24

Equation to work out moles of a gas

Mols of a gas = volume (cm3) / 24000 (cm3)

25

What is a redox reaction?

A reaction in which one species is oxidised and another is reduced

26

What is oxidation

The loss of electrons, loss of hydrogen, addition of oxygen

27

What is reduction

The gain of elections, addition of hydrogen, loss of oxygen

28

What is the full equation for magnesium + copper oxide

Mg + CuO = MgO + Cu

29

What is the ionic equation for magnesium + copper oxide

Mg + Cu 2+ = Mg 2+ + Cu

30

In magnesium + copper oxide what is the reducing agent?

Magnesium is oxidised so is therefore the reducing agent