Conservation of Mass & Balanced Chemical Equations Flashcards

All 6 cards in this deck

State the law of conservation of mass.

No atoms are lost or made during a chemical reaction, so the mass of the products equals the mass of the reactants.

Why must a symbol equation be balanced?

Because no atoms are lost or made, so there must be the same number of atoms of each element on both sides.

True or false? When balancing an equation you may change a subscript inside a formula to make the atoms balance.

False. Only the large multipliers in front of formulae may be changed; changing a subscript changes the substance.

What are the steps to balance a symbol equation?

e.g. $\mathrm{Ba} + \mathrm{HCl} \rightarrow \mathrm{BaCl_2} + \mathrm{H_2}$

1. Count atoms of each element on both sides: Cl is 1 on the left, 2 on the right.
2. Put a large multiplier in front of a whole formula: $2\mathrm{HCl}$.
3. Re-count until every element matches: $\mathrm{Ba} + 2\mathrm{HCl} \rightarrow \mathrm{BaCl_2} + \mathrm{H_2}$

How many atoms of each element are shown by a normal-script multiplier in front of a formula?

e.g. $3\mathrm{H_2O}$

The multiplier multiplies every atom in the formula — $3\mathrm{H_2O}$ is 6 hydrogen atoms and 3 oxygen atoms.

True or false? In a sealed (closed) container, the total mass does not change during a chemical reaction.

True. No atoms are lost or made and nothing can escape, so the mass stays the same.