Flashcards in Topic 3 - Quantitative Chemistry Deck (16):

1

## What is the relative formula mass of a substance?

### All of the atomic masses added together

2

## What is the law of conservation of mass?

### No atoms can be lost or gained in a chemical reaction

3

## How can we use the law of conservation of mass to work out the amount of reactant used when given the masses of the products?

### Add the masses of the products together

4

## Why might there be a change in mass in a reaction?

### It took place in a non-enclosed system

5

## How do you work out the uncertainty of a set of results?

### The uncertainty is half the range. e.g. find the mean of the results (24), take the smallest from the biggest (25-23 = 2), divide this by two (1). This would be written as - 24 +/- 1

6

## What is the Avogadro constant?

### The number of particles in one mole of a substance is 6.02x10^23

7

## Calculate the number of oxygen atoms in 0.5mol of O2

###
6.02x10^23 x 0.5 x 2

3.01x10^23 x 2

6.02x10^23

8

## How do you work out the mass in regards to the mole?

### mass = relative formula mass x mol

9

## How do you work out the equation for a reaction when given the masses?

### Calculate the amount of moles in each substance. Divide both by the smaller amount

10

## What is the limiting reactant?

### The reactant that is all used up

11

## How do you work out the concentration?

### Concentration in mol/dm^3 = amount of substance (mol)/ volume (dm^3)

12

## How do you convert mol/dm3 to g/dm3 and vice versa

### Multiply (to g/dm3) by relative formula mass. Divide by rfm for opposite.

13

## How do you work out the atom economy?

### (total Mr of desired product/total Mr of all reactants) x 100

14

## How do you work out percentage yield?

### (mass of product made/maximum theoretical mass of product) x 100

15

## What is the theoretical yield?

### The maximum amount of product that can be made

16