How to predict the approximate ph of fairly concentrated aqueous solutions.

sodium + water → sodium hydroxide + hydrogen

Explanation:

1) The first part of the statment "sodium combines with water" means that these two pure substances are the reactants.

Sodium is an alkali metal (group 1: Li, Na, K, Rb, Cs, Fr).

A typical chemical property of the alkali metal elments is that they react violently with water fo form the corresponding hydroxide and hydrogen gas.

2) The next two words, "to produce ". indicates, precisely, that what follow is the product of the reaction. In the chemical reaction it is indicated by the arrow →

3) Finally, you are told the products of the reaction: sodium hydroxide and hydrogen gas.

4) The word equation then follows the order reactants → products, which in this case is the sodium + water → sodium hydroxide + hydrogen

5) Using chemical symbols and conventions, that is:

Na(s) + H₂O (l) → NaOH(aq) + H₂(g).