C5 Separate Chemistry 1 Flashcards Preview

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Flashcards in C5 Separate Chemistry 1 Deck (17):
1

Most metals are ___________ metals

Transition

2

Properties of transition metals?

Conduct electricity
Brittle
High melting point
malleable
Hard
Shiny

3

Oxidation of metals results in

Corrosion

4

What are the two ways of preventing rust?

The barrier method and the sacrificial method

5

Explain how the barrier method prevents rusting

Painting/coating with plastic/oiling/greasing

All work by preventing water and oxygen from reaching the iron

6

Explain the sacrificial method

More reactive metal than iron – the water and oxygen react with this sacrificial metal instead of with the iron

7

What is galvanisation?

An object can be galvanised by spraying it with a coating of zinc. Zinc layer is firstly protective, but if it is scratched, the zinc around the site of the scratch works as a sacrificial metal

Galvanisation is protection + sacrificial

8

How does electroplating improve the appearance and/ or the resistance to corrosion

Uses electrolysis to reduce metal ions onto an iron electrode. It can be used to cut the iron with a layer of a different metal that won't be corroded away

9

Why are alloys stronger than pure metals?

In pure metals atoms are all the same and so the layers can slide over each other

In alloys the atoms are of different sizes, there is no sliding and so they are stronger

10

Why is iron alloyed with other metals to produce alloy steels?

-carbon is addd to iron to make steel
-this is done because iron is too soft for some things e.g. Drill bits
- steel is inflexible, strong, corrosion resistant and harder

11

Explain how to go from mol/dm^3 --> g/dm^3

1. Work it out in mol/dm^3 (DO # of MOL DIVIDED BY VOLUME)

2. Convert into grams by using:
Mass in grams = mol x Mr

12

Explain how to conduct a titration

1. Add set volume of alkali to a conical flask (and 3 drops of indicator)
2. Fill burette with an acid with a known concentration , record volume
3. Add acid to alkali bit by bit (swirling constantly)
4. INDICATOR COLOUR CHANGE
5. Record final volume, calculate the volume of acid used to neutralise the alkali


13

State the colour changes to look for with the 3 indicators


ACID TO ALKALI

Litmus: pink to purple

Methyl orange: pink to yellow

Phenolphthalein: colourless to pink

14

Explain how to improve the accuracy of the titration

Do you a rough titration to get an approximate idea of where the solution changes colour

Then repeat the whole thing a few times making sure you get same answer each time within 0.10 cm^3. CONCORDANT RESULTS

Finally calculate the mean of your results ignoring any anomalies

15

Why is universal indicator not appropriate for titrations?

It is used to estimate the pH of the solution because it content variety of colours each colour indicates a change of PH

But during a titration between and alkali and acid you want to see A certain colour change at the end point so you need to use a single indicator

16

What is the formula for percentage yield?

Percentage yield = mass of actual yield/mass of theoretic yield

Then multiply answer by 100 to get a percentage

17

Explain the causes of an actual yield which is less than 100%

1.reversible reaction?
2.side reactions (react and reactants might react with gases in the air to form extra products)
3.loss of product through transfer e.g. Pouring