Quantitative Chemistry Flashcards
(10 cards)
What is the law of conservation of mass?
No atoms are lost or made during a reaction, so the mass of reactants = mass of products.
What must be true about a balanced chemical equation?
The number of atoms of each element must be the same on both sides.
How is relative formula mass (Mr) calculated?
Sum of the relative atomic masses (Ar) of the atoms in the formula.
What is the Mr of HCl?
1 + 35.5 = 36.5.
How does Mr relate to balanced equations?
The sum of Mr for reactants must equal the sum of Mr for products (mass is conserved).
Why might a reaction appear to change mass?
A gas may have been released or gained and not accounted for in the measurement.
Example: Why does the mass increase when a metal reacts with oxygen?
Oxygen from the air combines with the metal to form a metal oxide, adding mass.
What is measurement uncertainty?
Small variations in a measurement due to limitations of equipment or human error.
How do you calculate uncertainty?
± 0.5 x Resolution
What should you do when recording measurements?
Consider and estimate uncertainty to improve accuracy.
