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Chemistry Core Knowledge C3 and C4 > C3 NEW > Flashcards

Flashcards in C3 NEW Deck (18)
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1

What is the law of the conservation of mass?

No atoms are lost or made during a chemical reaction. Mass of products = mass of reactants.

2

Define relative atomic mass (Ar).

The mass of an atom compared to 1/12 of the mass of a carbon-12 atom?

3

Define relative formula mass (Mr).

The sum of the relative atomic masses of the atoms in the numbers shown in the formula.

4

How can % by mass of an element in a compound be calculated?

= total mass of element / Mr x100

5

Why does mass seem to change in some reactions?

One or more of the reactants or products is a gas and the mass of the gas is not often measured.

6

What is concentration of a solution?

The amount of chemical dissolved in a certain volume of solution.

7

How is volume in cm3 changed to be in dm3?

Divided by 1000.

8

What unit is used for mass concentration?

g/dm3

9

What is the formula used to calculate concentration?

Concentration = mass(g) / volume(dm3)

10

Why might a reaction not have 100% yield?

-Reaction may be reversible
-Some of product may be lost
-Some of reactants May react differently

11

What does atom economy measure?

The amount of reactants that end up as useful products in a reaction.

12

Why are reactions with high atom economy preferred?

Less reactants are needed and have less waste so they are more sustainable and economic.

13

What is a limiting reagent?

Chemical used up in a reaction that limits the amount of product formed.

14

How many particles are in a mole of a substance?

The avagadro constant ( 6.02 x |0 23)

15

What is the formula to calculate moles from mass?

Moles = Mass divided by relative formula mass

16

How is molar concentration calculated?

Concentration = moles of solute (mol/dm3)

17

What experimental technique is used to get data to calculate the concentration of a solution?

Titration

18

What is the volume of 1 mole of any gas at room temperature and pressure?

24 dm3