Glucose, also known as "blood sugar" when measured in blood, has the formula $\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6$. (a) Write the equation for the combustion of glucose with $\mathrm{O}_2$ to give $\mathrm{CO}_2$ and $\mathrm{H}_2 \mathrm{O}$. (b) If 3.8 kcal is released by combustion of each gram of glucose, how many kilojoules are released by the combustion of 1.50 mol of glucose? (c) What is the minimum amount of energy a plant must absorb to produce 15.0 g of glucose?

Nitrogen in air reacts at high temperatures to form $\mathrm{NO}_2$ according to the following reaction: $\mathrm{N}_2+2 \mathrm{O}_2 \longrightarrow 2 \mathrm{NO}_2$ (a) Draw structures for the reactant and product molecules indicating single, double, and triple bonds. (b) Estimate $\Delta H$ for this reaction using the bond energies from above Table.

When organic compounds are burned without enough oxygen, carbon monoxide is formed as a product instead of carbon dioxide. Write and balance the combustion reactions from above Problem using CO as a product instead of $\mathrm{CO}_2$.

Acetylene $(\mathrm{H}-\mathrm{C} \equiv \mathrm{C}-\mathrm{H})$ is the fuel used in welding torches.

(a) Write the balanced chemical equation for the combustion reaction of $1 \mathrm{~mol}$ of acetylene with $\mathrm{O}_2(\mathrm{g})$ to produce $\mathrm{CO}_2(\mathrm{g})$ and water vapor.

(b) Estimate $\Delta H$ for this reaction (in $\mathrm{kJ} / \mathrm{mol}$ ) using the bond energies listed in the previous table.

(c) Calculate the energy value (in $\mathrm{kJ} / \mathrm{g}$) for acetylene. How does it compare to the energy values for other fuels in the previous table?

$$\mathrm{kJ} / \mathrm{g}$$

Converting liquid water to solid ice releases 6.02 kJ/mol. (a) What is the sign of $\Delta H$ for this process? Write a reaction showing heat as a product or reactant. (b) How many kilojoules are released by freezing 2.5 mol of $\mathrm{H}_2 \mathrm{O}$ ? (c) How many kilojoules are released by freezing 32 g of $\mathrm{H}_2 \mathrm{O}$ ? (d) How many kilojoules are absorbed by melting 1 mol of ice?

The vaporization of $\mathrm{Br}_2$ from the liquid to the gas state requires 31.0 kJ/mol. (a) What is the sign of $\Delta H$ for this process? Write a reaction showing heat as a product or reactant. (b) How many kilocalories are needed to vaporize 5.8 mol of $\mathrm{Br}_2$ ? (c) How many kilojoules are needed to evaporate 82 g of $\mathrm{Br}_2$ ?

Balance the following equation for the synthesis of hydrazine, $\mathrm{N}_2 \mathrm{H}_4$, a substance used as rocket fuel.

$$\mathrm{NH}_3(g)+\mathrm{Cl}_2(g) \longrightarrow \mathrm{N}_2 \mathrm{H}_4(l)+\mathrm{NH}_4 \mathrm{Cl}(s)$$

What is meant by the term heat of reaction? What other name is a synonym for this term?

Is the total enthalpy of the reactants for an endothermic reaction greater than or less than the total enthalpy of the products?

Write the electron configuration of potassium, Z=19, and show how a potassium atom can attain a noble gas configuration.

Which structure is known as the "pacemaker" of the heart?

Does hypercapnia and acidosis have positive chronotropic effects?

Which of the following will not increase the heart rate?

a) Decreased blood oxygen

b) Increased blood carbon dioxide

c) Increased blood pressure

d) Decreased blood pH

Carbon dioxide is a nonpolar molecule, whereas sulfur dioxide is polar. Draw Lewis structures for each of these molecules to explain this observation.