Questions: Question 18 (1 point) If an element is higher on the reactivity table than another species it is replacing, then the reaction will occur. True False Question 19 (1 point) What is the coefficient of H2O when the following equation is correctly balanced? Ca + H2O -> Ca(OH)2 + H2 2 1 4

Solution Steps

The statement in Question 18 is about the reactivity series, which is a list of elements ordered by their ability to displace other elements in compounds. If an element is higher on the reactivity series than another element it is replacing, the reaction will occur. This is a fundamental principle in chemistry regarding single displacement reactions.

Based on the explanation in Step 1, the statement is true. If an element is higher on the reactivity table than the species it is replacing, the reaction will indeed occur.

The given chemical equation is: \[ \mathrm{Ca} + \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{Ca}(\mathrm{OH})_{2} + \mathrm{H}_{2} \]

To balance the equation, ensure that the number of each type of atom is the same on both sides of the equation.

1. Calcium (Ca): 1 atom on both sides.
2. Hydrogen (H): 2 atoms in \(\mathrm{H}_{2}\) and 2 in \(\mathrm{H}_{2}\mathrm{O}\) on the left, totaling 4. On the right, there are 2 in \(\mathrm{Ca}(\mathrm{OH})_{2}\) and 2 in \(\mathrm{H}_{2}\), totaling 4.
3. Oxygen (O): 1 atom in \(\mathrm{H}_{2}\mathrm{O}\) on the left and 2 in \(\mathrm{Ca}(\mathrm{OH})_{2}\) on the right.

To balance the oxygen atoms, place a coefficient of 2 in front of \(\mathrm{H}_{2}\mathrm{O}\): \[ \mathrm{Ca} + 2\mathrm{H}_{2}\mathrm{O} \rightarrow \mathrm{Ca}(\mathrm{OH})_{2} + \mathrm{H}_{2} \]

Now, the equation is balanced with:

• 1 Calcium (Ca) on both sides.
• 4 Hydrogen (H) on both sides.
• 2 Oxygen (O) on both sides.

From the balanced equation, the coefficient of \(\mathrm{H}_{2}\mathrm{O}\) is 2.

Final Answer