Quanitative chemistry Flashcards
Why is mass conserved?
No atoms are added or taken away from the system, so the mass stays the same.
What is the relative formula mass?
It is the sum of the relative atomic masses of the atoms in the numbers shown in the formula .
How do you calculate the relative mass of products and reactants?
Add the atomic masses together for both reactants and products. They should be the same because of the law of conservation of mass.
Explain how the mass can change in non-enclosed system reactions.
Substances can enter or leave a non-enclosed system. If a gas escapes, the total mass will look as if it has decreased. If a gas is gained, the total mass will look as if it has increased. However, the total mass stays the same if the mass of the gas is included.
Why is when a measurement is made there is always some uncertainty about the result obtained?
Whether a thermometer is inaccurate (showing a temperature of 24.0°C, 24.5°C or 25.0°C)>
Or
You do not know exactly when a chemical reaction has finished
What is a mole?
A mole corresponds to the mass of a substance that contains 6.023 x 1023 particles of the substance.
How do you find out how many moles there are?
Moles = mass
——————–
atomic mass
How do you work out the mass of a solute in a solution?
MASS OF SOLUTE = CONCENTRATION X VOLUME
How do you use relative formula mass to find out how many moles or mass of a substance?
MASS = MOLES X RELATIVE FORMULA MASS
