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
