Problem 74 - Chemistry The Central Science

Question

Write a balanced equation for the reaction that occurs in each of the following cases: (a) Cesium is added to water. (b) Strontium is added to water. (c) Sodium reacts with oxygen. (d) Calcium reacts with iodine.

Step-by-Step Solution

Answer

(a) \( 2Cs + 2H_2O \rightarrow 2CsOH + H_2 \) (b) \( Sr + 2H_2O \rightarrow Sr(OH)_2 + 2H_2\) (c) \( 4Na + O_2 \rightarrow 2Na_2O \) (d) \( Ca + I_2 \rightarrow CaI_2 \)

Step 1: Write the unbalanced equation

Cesium (Cs) reacts with water (H2O) to form cesium hydroxide (CsOH) and hydrogen gas (H2). Cs + H2O -> CsOH + H2

Step 2: Balance the equation

Checking the number of atoms on each side of the equation, we need to put a coefficient of 2 in front of CsOH to balance cesium and a coefficient of 2 in front of H2O to balance hydrogen and oxygen atoms. 2Cs + 2H2O -> 2CsOH + H2 So, our final balanced equation is: \[ 2Cs + 2H_2O \rightarrow 2CsOH + H_2 \] (b) Strontium is added to water.

Step 1: Write the unbalanced equation

Strontium (Sr) reacts with water (H2O) to form strontium hydroxide (Sr(OH)2) and hydrogen gas (H2). Sr + H2O -> Sr(OH)2 + H2

Step 2: Balance the equation

Looking at the atoms in the equation, the strontium and oxygen atoms are already balanced. To balance the hydrogen atoms, we need to put a coefficient of 2 in front of H2O and H2. Sr + 2H2O -> Sr(OH)2 + 2H2 The final balanced equation is: \[ Sr + 2H_2O \rightarrow Sr(OH)_2 + 2H_2\] (c) Sodium reacts with oxygen.

Step 1: Write the unbalanced equation

Sodium (Na) reacts with oxygen (O2) to form sodium oxide (Na2O). Na + O2 -> Na2O

Step 2: Balance the equation

To balance this equation, place a coefficient of 4 in front of Na and a coefficient of 2 in front of Na2O. 4Na + O2 -> 2Na2O Our final balanced equation is: \[ 4Na + O_2 \rightarrow 2Na_2O \] (d) Calcium reacts with iodine.

Step 1: Write the unbalanced equation

Calcium (Ca) reacts with iodine (I2) to form calcium iodide (CaI2). Ca + I2 -> CaI2

Step 2: Balance the equation

This equation is already balanced, as there is an equal number of each type of atom on both sides. Our final balanced equation is: \[ Ca + I_2 \rightarrow CaI_2 \]

Key Concepts

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships of the substances used and produced by chemical reactions.

Chemical Reactions

Chemical reactions involve the breaking and forming of bonds between atoms to produce new substances. During a chemical reaction, the identities of substances change as atoms are rearranged. Knowledge of how to write balanced chemical equations is crucial because it reflects the law of conservation of mass, where the total mass of reactants equals the total mass of products.

Compounds and Elements

Elements are pure substances consisting of only one type of atom, while compounds are substances composed of two or more different elements that are chemically bonded. The process of a chemical reaction often involves elements reacting to form compounds, or compounds breaking down into elements or smaller compounds.