Problem 71 - Chemistry: The Central Science

Question

Complete and balance the following equations: (a) \(\mathrm{ZnCO}_{3}(s) \stackrel{\Delta}{\longrightarrow}\) (b) \(\mathrm{BaC}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow\) (c) \(\mathrm{C}_{2} \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow\) (d) \(\mathrm{CS}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow\) (e) \(\mathrm{Ca}(\mathrm{CN})_{2}(s)+\mathrm{HBr}(a q) \longrightarrow\)

Step-by-Step Solution

Answer

(a) \[\mathrm{ZnCO}_{3}(s) \stackrel{\Delta}{\longrightarrow} \mathrm{ZnO}(s) + \mathrm{CO}_{2}(g)\] (b) \[\mathrm{BaC}_{2}(s) + 2\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{2}(g) + \mathrm{Ba(OH)}_{2}(s)\] (c) \[2\mathrm{C}_{2} \mathrm{H}_{2}(g) + 5\mathrm{O}_{2}(g) \longrightarrow 4\mathrm{CO}_{2}(g) + 2\mathrm{H}_{2} \mathrm{O}(l)\] (d) \[\mathrm{CS}_{2}(g) + 3\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g) + 2\mathrm{SO}_{2}(g)\] (e) \[\mathrm{Ca}(\mathrm{CN})_{2}(s) + 2\mathrm{HBr}(a q) \longrightarrow \mathrm{CaBr}_{2}(a q) + 2\mathrm{HCN}(a q)\]

Step 1: (a) Determine the products

For the first reaction, we have ZnCO_3(s), which decomposes when heated (indicated by the delta sign). As it is a carbonate compound, it will decompose into a metal oxide and carbon dioxide gas when heated. In this case, the metal is zinc, so the products will be zinc oxide (ZnO) and carbon dioxide gas (CO_2).

Step 2: (a) Balance the equation

Now, let's balance the equation. Since there is only 1 Zn, 1 C, and 3 O atoms on both sides of the equation, we don't need to add any coefficients. The balanced equation for (a) is: \[\mathrm{ZnCO}_{3}(s) \stackrel{\Delta}{\longrightarrow} \mathrm{ZnO}(s) + \mathrm{CO}_{2}(g)\]

Step 3: (b) Determine the products

In the second reaction, we have barium carbide (BaC_2) and water (H_2O) as reactants. Barium carbide reacts with water to produce acetylene gas (C_2H_2) and barium hydroxide (Ba(OH)_2).

Step 4: (b) Balance the equation

To balance this equation, we need to add a coefficient of 2 in front of the H_2O, since there are 2 O and 4 H atoms on the product side. The balanced equation for (b) is: \[\mathrm{BaC}_{2}(s) + 2\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{2}(g) + \mathrm{Ba(OH)}_{2}(s)\]

Step 5: (c) Determine the products

In the third reaction, we have acetylene gas (C_2H_2) reacting with oxygen gas (O_2). This is a combustion reaction and will produce carbon dioxide (CO_2) and water (H_2O) as products.

Step 6: (c) Balance the equation

To balance this equation, we add a coefficient of 2 in front of the CO_2 and O_2 and a coefficient of 1 in front of H_2O. The balanced equation for (c) is: \[2\mathrm{C}_{2} \mathrm{H}_{2}(g) + 5\mathrm{O}_{2}(g) \longrightarrow 4\mathrm{CO}_{2}(g) + 2\mathrm{H}_{2} \mathrm{O}(l)\]

Step 7: (d) Determine the products

In the fourth reaction, we have carbon disulfide (CS_2) reacting with oxygen gas (O_2). This is another combustion reaction and will produce carbon dioxide (CO_2) and sulfur dioxide (SO_2) as products.

Step 8: (d) Balance the equation

To balance this equation, we add a coefficient of 1 in front of CS_2, 3 in front of O_2, and 2 in front of SO_2. The balanced equation for (d) is: \[\mathrm{CS}_{2}(g) + 3\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g) + 2\mathrm{SO}_{2}(g)\]

Step 9: (e) Determine the products

In the last reaction, we have calcium cyanamide (Ca(CN)_2) reacting with hydrobromic acid (HBr). This is an acid-base reaction and will produce calcium bromide (CaBr_2) and hydrogen cyanamide (HCN) as products.

Step 10: (e) Balance the equation

To balance this equation, we add a coefficient of 2 in front of the HBr and HCN. The balanced equation for (e) is: \[\mathrm{Ca}(\mathrm{CN})_{2}(s) + 2\mathrm{HBr}(a q) \longrightarrow \mathrm{CaBr}_{2}(a q) + 2\mathrm{HCN}(a q)\]