Final answer:
Magnesium oxide (MgO) is a base because it can form Mg(OH)2 when reacted with water, which provides OH- ions. It is not a fuel in its oxide form, nor is it an acid since it doesn't donate H+ ions.
Step-by-step explanation:
Magnesium oxide (MgO) is an ionic compound that is considered a base when dissolved in water, as it can provide OH- ions to the solution. Although similar to magnesium hydroxide (Mg(OH)2), which is also a base and commonly used in antacids, magnesium oxide itself does not directly contain the OH- ions in its formula. However, when it reacts with water, it can form Mg(OH)2, which is an Arrhenius base due to the presence of OH- ions. Moreover, magnesium is a component in various compounds that can serve as fuel when it burns brightly, as in flares and fireworks, but in the case of magnesium oxide, it is known as a base and not as a fuel. Acids, on the other hand, are substances that can donate H+ ions, which magnesium oxide cannot do, hence it is not an acid.