Quantitve Chemistry

Question 1

What is the law of conservation of mass

Answer 1

No atoms are lost or made during a chemical reactions
This means that chemical reactions should always be balanced

Question 2

What is the formula for the law of conservation of mass

Answer 2

Total mass of reactants=total mass of products

Question 3

How do you calculate the relative formula mass

Answer 3

By adding up the atomic masses of the atoms

Question 4

How could substances lose or gain mass during a reaction

Answer 4

A reactant or product is a gas and it’s mass had not been taken into account

Question 5

What is uncertainty

Answer 5

There is always uncertainty when making a measurement in chemistry.

Question 6

What is the uncertainty on a digital measuring instrument

Answer 6

Half the last digit shown on display

Question 7

What will the uncertainty for a thermometer

Answer 7

Estimated as plus or minus half the smallest scale division.

Question 8

How do you calculate the uncertainty

Answer 8

Half the range
Range = biggest value - smallest value

Question 9

What is the chemical equation for moles

Answer 9

Moles=mass divided by relative formula mass

Question 10

What is the difference between molecular vs empirical formula

Answer 10

Molecular-shows the actual amount of atoms which make up a molecule
For example glucose = C6 H12 O6

Question 11

What is the difference between the molecular vs the empirical formula

Answer 11

Shows the simplest ratio of atoms which make up a molecule
For example glucose= CH2O

Question 12

What is a limiting reactant

Answer 12

The reactant that is used up/ not in excess during a reaction

Question 13

Why do we use an excess reactant to react with the limiting reactant

Answer 13

The amount of product produced is restricted to the amount of the excess reactant that reacts with the limiting one

Question 14

What are the units for the concentration of a solution

Answer 14

g/dm3

Question 15

How do you calculate the concentration of a solution

Answer 15

Mass of solute divided by volume
A smaller volume of larger mass gives a higher concentration
A larger volume or smaller mass gives a lower comcentration

Question 16

What is the mass of one mole equal to

Answer 16

The relative formula mass

Question 17

What does one mole of a substance contain

Answer 17

The same number of the stated particles, atoms, molecules or ions as one mole of any other substance

Question 18

What is avogrados constant

Answer 18

The number of atoms, molecules or ions of a given substance. It is 6.02 x 10^23

Question 19

What is an example of using moles to interpret equations

Answer 19

Mg+2HCl-» MgCl2+H2 shows that 1 mol of Mg reacted with 2 moles of HCl to produce 1 mol of MgCl2 with 1 mol of H2

Question 20

How do you use moles to balance equations

Answer 20

1)convert the masses in grams to amounts of moles
2) converting the numbers of moles to simple whole number ratios