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Chemistry mistakes > Period 3 > Flashcards

Period 3 Flashcards

1
Q

Describe a method for determining the melting point of the sample

A

Sample in melting point apparatus
Heat slowly to establish melting point range
Lower melting point indicates presence of impurities

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2
Q

Describe a test you could carry out in a test tube to distinguish between Na2O and P4O10

A

React with water
Add litmus paper and universal indicator and measure pH
NaOH 12-14 pH
H3PO4 0-2 pH

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3
Q

Write ionic equation for P4O10 with excess NaOH

A

P4O10 + 12OH- -> 4PO43- + 6H2O

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4
Q

Write the two equations to show amphoteric nature of Al2O3

A

Al2O3 + 6HCl -> 2AlCl3 + 3H2O
Al2O3 + 2NaOh +3H2O -> 2NaAl(OH)4

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5
Q

Explain using an equation why SiO2 is classified as an acidic oxide

A

Reacts with alkalis
SiO2 + 2NaOH -> Na2SiO3 + H2O

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6
Q

Give two physical properties of SiO2

A

Insoluble
Hard
High melting point

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7
Q

Write an equation when ions are formed when SO2 reacts with water

A

SO2 + H2O -> H+ + HSO3-

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8
Q

Suggest why white phosphorus is stored under water

A

Prevents reacting with air

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9
Q

Suggest why it is usually represented by P4O10 rather than P2O5

A

Molecular formula is P4O10

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10
Q

Explain why an excess of MgO can be used for this neutralisation

A

MgO is sparingly soluble

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11
Q

Observations when Mg burns in O2

A

Bright white flame
White fumes

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12
Q

Observations when S burns in O2

A

Blue flame
Misty fumes

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13
Q

How to show Al2O3 has ions

A

Heat until molten
Conducts electricity

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14
Q

Why a thin layer of Al2O3 protects Al from corrosion in moist air

A

Insoluble in water

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15
Q

Ionic equation to show Al2O3 reacting with HCl

A

Al2O3 + 6H+ -> 2Al3+ + 3H2O

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16
Q

Ionic equation to show Al2O3 reacting with aquatic NaOH

A

Al2O3 + 2OH- + 3H2O -> 2Al(OH)4-

17
Q

Equation if SiO2 and NaOH

A

SiO2 + NaOH -> Na2SiO3 + H2O

18
Q

Which element forms an ionic oxide that reacts with strong alkalis

A

Aluminium

19
Q

Predict whether melting point of Lithium oxide is higher than or lower Na2O

A

Higher
Li+ smaller than Na+
Attracts O2- ion more strongly

Chemistry mistakes (27 decks)

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