I- Period 3 =)

Question 1

Write an equation for the reaction between Na2O and P4O10.
State the general type of reaction illustrated by this example. (2)

Answer 1

6Na2O + P4O10 –> 4Na3PO4

Question 2

Silicon dioxide does not react with hydrochloric acid but it does react with sodium hydroxide.
State one property of silicon dioxide that can be deduced from this information and write an equation for its reaction with sodium hydroxide. (2)

Answer 2

• acidic
• SiO2 + 2NaOH → Na2SiO3 + H2O

Question 3

When a piece of sodium is added to 200 cm3 of water in a large beaker a vigorous reaction occurs. The temperature of the water increases by 25 oC.
Suggest why it is dangerous to react a similar piece of sodium with 10 cm3 of water in a boiling tube. (1)

Answer 3

temp will ↑ more/ reactants can shoot out of tube

Question 4

Give an equation for the reaction of phosphorus(V) oxide with water.
Suggest a pH for the solution formed. (2)

Answer 4

P4O10 + H2O –> H3PO4
pH 0

Question 5

Explain, in terms of crystal structure and bonding, why silicon(IV) oxide has a higher melting point than phosphorus(V) oxide. (4)

Answer 5

• SiO2- macromolecular
• strong covalent bonds betw atoms
• P4O10- molecular
• weak vdW betw molecules- easy to break

Question 6

Give an equation and two observations made for the reaction that occurs when sodium is heated in oxygen. (2)

Answer 6

4Na + O2 –> 2Na2O
1. yellow flame
2. white solid/ powder

Question 7

Explain the increase in melting point from sodium oxide to magnesium oxide. (2)

Answer 7

• Mg2+ has ↑ charge (/ smaller ion)
• ↑ attraction betw Mg2+ & O2-/ stronger ionic bond

Question 8

A sample of the highest oxide of phosphorus was prepared in a laboratory.
Describe a method for determining the melting point of the sample.
State how the result obtained could be used to evaluate its purity. (3)

Answer 8

1. sample in capillary in oil bath/ Thiele tube
2. heat slowly/ gradually to establish mp range
3. if mp < data book value (/ broad range) indicates impurity

Question 9

Which element forms an ionic oxide that reacts with strong alkalis?
A. Aluminium
B. Magnesium
C. Sodium
D. Sulfur

Answer 9

A!!!!!

Al oxide is ionic, chloride is covalent

Question 10

Give an equation for the reaction of phosphorus (V) oxide with sodium hydroxide solution. (1)

Answer 10

P4O10 + 12NaOH –> 4Na3PO4 + 6H2O

Question 11

Describe a test you could carry out in a test tube to distinguish between sodium oxide and phosphorus oxide. (3)

Answer 11

• add water
• universal indicator
• blue for Na2O; red for P4O10

Question 12

Write an equation for the reaction of sulfur trioxide with potassium hydroxide solution. (1)

Answer 12

SO3 + 2KOH –> K2SO4 + H2O

Question 13

Sodium oxide forms a solution with a higher pH than magnesium oxide when equal amounts, in moles, of each oxide are added separately to equal volumes of water.
State why both oxides form alkaline solutions.
Suggest why sodium oxide forms a solution with a higher pH than the solution formed from magnesium oxide. (2)

Answer 13

• forms OH- ions
• NaOH ↑ soluble than Mg(OH)2

Question 14

Give an equation and one observation made for the reaction that occurs when phosphorus is heated in oxygen. (2)

Answer 14

• P4 + 5O2 –> P4O10
• white flame/ white fumes/ solid

Question 15

Suggest why Al(OH)3 is insoluble in water. (1)

Answer 15

strong covalent bonds

Question 16

Explain why sodium oxide forms an alkaline solution when it reacts with water. (2)

Answer 16

• O2- ions in Na2O
• react w/ H2O –> OH- ions