Oxides from alkali to acid

Science · Chemistry · ages 16-18

Name ______________________ Date ____________

Sulfur trioxide shaken with water gives...
- An alkali
- An acidic solution of sulfuric acid
- A salt only
Sodium oxide shaken with water gives...
- An acidic solution
- Nothing at all
- An alkaline solution of sodium hydroxide
Aluminium oxide reacts with both acids and alkalis.
Circle one: True False
Magnesium oxide shaken with water gives a solution of pH...
- Below 7
- Exactly 7
- Above 7
Why does the row shift from basic to acidic oxides?
- Bonding shifts from ionic to covalent
- Atoms grow bigger along the row
- All oxides dissolve equally
Phosphorus(V) oxide shaken with water gives a solution of pH...
- Above 7, like a metal oxide
- Near 7, since it will not dissolve
- Below 7, like a non-metal oxide
A student calls aluminium oxide neutral since it barely shifts pH. What is wrong?
- It is strongly acidic instead
- It never reacts with anything
- It is amphoteric: it reacts with both acids and alkalis
Phosphorus(V) oxide and magnesium oxide each meet water. Which pairing is right?
- Both give alkaline solutions
- P oxide acidic from covalent bonding, MgO alkaline from ionic bonding
- Both give acidic solutions

Answer key

For grown-ups. Fold this page away before handing over the rest.

An acidic solution of sulfuric acid · The covalent oxide dissolves into an acid.
An alkaline solution of sodium hydroxide · The ionic oxide dissolves into hydroxide ions.
True · That two-way behaviour is exactly what amphoteric means.
Above 7 · Left-side metal oxides turn water alkaline.
Bonding shifts from ionic to covalent · Ionic oxides free hydroxide; covalent ones free hydrogen ions.
Below 7, like a non-metal oxide · Right-side covalent oxides turn water acidic.
It is amphoteric: it reacts with both acids and alkalis · Little pH shift hides two-way reactivity.
P oxide acidic from covalent bonding, MgO alkaline from ionic bonding · Bonding decides: covalent right goes acid, ionic left goes alkali.