xxx Flashcards by Leah Dann | Brainscape

Q

What is the relative mass of a neutron?

A

1.

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Q

What is an atoms mass number?

A

Number of protons and neutrons in the nucleus.

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Q

What is an isotope?

A

Element with same number of protons but different number of neutrons.

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Q

Calculate the relative formula mass for carbon dioxide?

A

12+16+16=24.

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Q

What is meant by the term mole?

A

The relative formula mass of a substance in grams is one mole.

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Q

Calculate the percentage by mass of carbon in carbon dioxide?

A

Ar of carbon = 12
Mr of carbon = 44
12 divided by 44 times 100 = 27.3%

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Q

How many atoms of sodium react with 1 molecule of chlorine to make 2 sodium chlorides?

A

2.

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Q

What is meant by the term yield?

A

Amount of useful product obtained from a reaction.

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Q

Give reasons to explain why the yield of a reaction may be less than expected?

A

Reaction may be incomplete.
Some product is lost.
Other unwanted reactions may occur making a different product.
Reaction may be reversible.

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Q

What is chromatography used for?

A

Separate mixtures.

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Q

Give an advantage and disadvantage for using gas chromatography over paper chromatography?

A

Advantage = Rapid, accurate, sensitive.
Disadvantage = Expensive.

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Q

What is a mass spectrometer used for?

A

Identify substances.

Measure a compound relative molecular mass.

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Q

How do you work out the rate of reaction?

A

Amount of reactant used or product formed divided by time.

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Q

What 2 things need to happen for particles to react?

A

Collide with enough energy.

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Q

What 4 ways speed up a chemical reaction?

A

Increase concentration.
Increase temperature.
Increase surface area.
Use a catalyst.

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Q

Why do catalysts not need to be replaced?

A

They are not used up or destroyed in a chemical reaction.

Q

What is the difference between exothermic and endothermic reactions?

A

Exothermic = gives out heat - temperature increases.
Endothermic = takes in heat - temperature decreases.

Q

Give a use for exothermic reactions?

A

Self heating cans/hand warmers.
Burning.
Thermal decomposition.

Q

In a reversible reaction 500 J of energy is releases in the forward reaction. What happens in the reverse reaction?

A

500 J of energy is absorbed.

Q

What is the pH of an acid?

A

1-6.

Q

What is the atomic number of magnesium?

A

12.

Q

Calculate the relative atomic mass of water?

A

H = 1
0 = 16
1+1+16=18

Q

How many atoms of calcium react with 1 molecule of chlorine to make calcium chloride?

A

1 atom.

Q

Calculate the percentage mass of oxygen in water?

A

Ar of oxygen = 16
Mr of water = 18
16 divided by 18 times 100 = 88.9%