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Chemistry > Quantitative chemistrt > Flashcards

Quantitative chemistrt Flashcards

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1
Q

How do you work out concentration?

A

Amount/volume

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2
Q

What is concentration measured in?

A

Mol/dm3

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3
Q

Hydrochloric acid is added to a strip of magnesium and a gas is released. Write the symbol equation for this.

A

HCl + Mg -> MgCl + H2

Mg= +2 ion
Cl= -1 ion

HCl + Mg -> MgCl2 + H2

Balanced:
2HCl + Mg -> MgCl2 + H2

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4
Q

Relative formula mass of sulphuric acid

A

98

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5
Q

What is moles?

A

Unit for amount of a substance

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6
Q

How many atoms are there in a mole?

A

6x10 23

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7
Q

Equation for moles

A

Moles= Mass/mr

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8
Q

Hydrogen peroxide (H2O2) decomposes into water and oxygen. How much oxygen gas will be given off from 40.8g of hydrogen peroxide?

A

H2O2 -> H2O + O2

Balanced:
2H2O2 -> 2H2O + O2

Mr
2H2O= 68
2H2O= 36
O2=32

  1. 8 -> ?
  2. 8 -> 19.2
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9
Q

Titration method

A

Pipette 25.0 cm3 of alkali into a conical flask, add a phenolphthalein indicator
Fill a burette with an acid of known concentration
Take the initial reading on the burette and record it
While swirling the flask, use the tap to slowly add the acid into the alkali
When the first permanent colour change (Pink -> Clear) Stop adding acid
Record the final volume in the burette, calculate the volume of acid to neutralise alkali using initial volume.
Make sure results are within 0.10 cm3.
Work out mean ignoring anomalous results

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10
Q

Properties of a strong acid

A 
Fully dissociate
HCl -> H+ + Cl-
Big difference between strength and concentration 
Hydrochloric 
Nitric 
Sulphuric
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11
Q

Properties of a weak acid

A

Partially dissociate

H2O reversible arrows H+ + OH-

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12
Q

True or false

Ionic Compounds have to be molten or dissolved to be able to conduct electrolysis

A

True

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13
Q

What is cryolite used for?

A

To reduce the melting point of molten aluminium

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14
Q

What is attracted to the cathode in aluminium electrolysis?

A

Al3 + 3e- -> Al

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15
Q

What is attracted to the anode in aluminium electrolysis?

A

2O2- 4e- -> O2

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16
Q

What element is the anode made of in aluminium electrolysis?

A

Carbon

17
Q

What gas is released at the anode in aluminium electrolysis?

A

Oxygen

18
Q

How is carbon dioxide produced in aluminium electrolysis?

A

The carbon anode reacts with the oxygen gas released

19
Q

What are the common set ups for electrolysis?

A

Sodium Chloride: H2 Cl2 NaOH

Sodium Sulphate H2 O2
Copper chlorideCu Cl2
Copper sulphate Cu O2

20
Q

What is the test for hydrogen gas?

A

Squeaky pop

21
Q

What is the test for oxygen gas?

A

Relighting glowing splint

22
Q

What is the test for chlorine?

A

Bleaches damp litmus paper

23
Q

Percentage yield

A

Actual yield/ Theoretical yield

What you made/ How much you thought you would make

24
Q

Atom economy

A

Mr of atoms in required products/ Mr reactants

25
Q

Titration calculations

A

Calculate number of moles of acid used
Use this to find the number of H+ ions involved in reactions
Equal to number of OH- ions involved in the reaction
Calculate number of moles alkalised
Calculate the concentration of alkali

Number of moles= concentration x volume
Number of moles= mass/Mr

26
Q

Example of titration calculation

A

25cm3 of NaOH was neutralised by 15cm3 of 0.2 mol/dm3 HCl, find the concentration of the alkali

Concentration alkali=X
Volume of alkali= 25cm3
Concentration acid= 0.2 mol/dm3
Volume of acid = 15cm3

Number of moles of acid= 0.2 x 0.015
=0.003

moles of alkali/volume= concentration

0.003/0.025 =0.12

27
Q

How much does 1 mole take up?

A

24dm3

28
Q

Electrolysis required practical

A

Aluminium extracted from ore bauxite by electrolysis. Bauxite contains aluminium oxide. Al2O3
Aluminium oxide has very high melting point, cryolite lowers melting point
Molten mixture contains free ions- conduct electricity
Positive Al3+ ions attracted to negative electrode where each pick up 3 electrons and turn into neutral aluminium atoms. Sink to bottom of electrolysis tank
Negative O2- ions attracted to positive electrode where lose 2 electrons. Neutral oxygen atoms combine to form O2 molecules.

29
Q

What does the law of conservation state?

A

no atoms are lost or made during chemical reactions, so the mass of the products equals the mass of the reactants

Chemistry (10 decks)

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