chemistry: quantitative chem paper 1

What is the law of conservation of mass?

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

What are the starting materials called?

Reactants.

What are the chemicals formed in a reaction called?

Products.

How are ionic compounds formed?

When metals react with non metals.

Do metals form positive or negative ions?

Postive

Do most non metals form positive ions or negative ions?

Negative.

What are non metal ions that are positively charged?

Hydrogen ion ( H+)

Ammonium (NH4+)

What happens to the charges in an ionic compound?

The charges on the ions cancel out. Leaving an overall charge of 0.

Why aren't you allowed to change the small number in a chemical formula?

It produces a different molecule.

What is the relative formula mass of a compound?

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

What is the relative formula mass symbol?

Mr

What are the units for relative formula mass

There isn't any

What is the equation to find the percentage by mass?

Total relative atomic mass of atoms of that element / relative formula mass of compound , x100

Where is the relative atomic mass located on the elements?

The top number

What is the equation to calculate number of moles?

Mass(g)/Relative atomic mass Ar

How do you find the mass (g) when given the number of moles and formula mass?

number of moles x formula mass mr

What is Avogadro's constant?

6.02 × 10²³ is one mole

How do you calculate the number of atoms on one mole?

Add up the atoms in the element/compound.

Multiply that by 6.02 × 10²³

What is the limiting reactant?

The reactant that is fully used up.

Why is more of one reactant than the other (mole) in an experiment?

To make sure all of an element reacts.

What is the excess reactant?

The reactant that is not fully used up.

How many moles of sodium chloride will be produced if we used 1 mole of sodium hydroxide and 0.25 moles of hydrochloric acid?

0.25 moles as it's limiting reactant.

What does the concentration tell you about a solute?

Tells us the mass of a solute in a given volume of solution.

What is a solute?

A chemical that is dissolved in a solvent.

What is the unit of concentration?

g/dm³

How do you calculate the concentration?

Mass(g)/Volume(dm³)

What happens to the concentration when we increase the mass of the solute and keep volume the same?

Concentration increases

What happens to the concentration when we increase the volume of solution and keep mass of solute the same?

Decrease the concentration