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Chapter 3: Problem 22

Determine the formula weights of each of the following compounds: (a) nitrous oxide, \(\mathrm{N}_{2} \mathrm{O},\) known as laughing gas and used as an anesthetic in dentistry; (b) benzoic acid, \(\mathrm{HC}_{7} \mathrm{H}_{5} \mathrm{O}_{2}\), a substance used as a food preservative; (c) \(\mathrm{Mg}(\mathrm{OH})_{2}\), the active ingredient in milk of magnesia; (d) urea, \(\left(\mathrm{NH}_{2}\right)_{2} \mathrm{CO}, \mathrm{a}\) compound used as a nitrogen fertilizer; (e) isopentyl acetate, \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{C}_{5} \mathrm{H}_{11}\), responsible for the odor of bananas.

Short Answer

Expert verified
The formula weights of the given compounds are as follows: (a) Nitrous oxide, $\mathrm{N}_{2} \mathrm{O}$: 44.013 g/mol (b) Benzoic acid, $\mathrm{HC}_{7} \mathrm{H}_{5} \mathrm{O}_{2}$: 122.123 g/mol (c) Magnesium hydroxide, $\mathrm{Mg}(\mathrm{OH})_{2}$: 58.319 g/mol (d) Urea, $\left(\mathrm{NH}_{2}\right)_{2} \mathrm{CO}$: 60.056 g/mol (e) Isopentyl acetate, $\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{C}_{5} \mathrm{H}_{11}$: 114.188 g/mol

Step by step solution

01

(a) Formula weight of Nitrous oxide (N2O)

: 1. Identify elements: Nitrogen (N) and Oxygen (O) 2. Atomic weights: Nitrogen (N) = 14.007, Oxygen (O) = 15.999 3. Multiply by the number of atoms: (2 × 14.007) + (1 × 15.999) 4. Formula weight of N2O = 28.014 + 15.999 = 44.013 g/mol
02

(b) Formula weight of Benzoic acid (HC7H5O2)

: 1. Identify elements: Hydrogen (H), Carbon (C), and Oxygen (O) 2. Atomic weights: Hydrogen (H) = 1.008, Carbon (C) = 12.011, Oxygen (O) = 15.999 3. Multiply by the number of atoms: (1 × 1.008) + (7 × 12.011) + (5 × 1.008) + (2 × 15.999) 4. Formula weight of HC7H5O2 = 1.008 + 84.077 + 5.040 + 31.998 = 122.123 g/mol
03

(c) Formula weight of Mg(OH)2

: 1. Identify elements: Magnesium (Mg), Oxygen (O), and Hydrogen (H) 2. Atomic weights: Magnesium (Mg) = 24.305, Oxygen (O) = 15.999, Hydrogen (H) = 1.008 3. Multiply by the number of atoms: (1 × 24.305) + (2 × 15.999) + (2 × 1.008) 4. Formula weight of Mg(OH)2 = 24.305 + 31.998 + 2.016 = 58.319 g/mol
04

(d) Formula weight of Urea ((NH2)2CO)

: 1. Identify elements: Nitrogen (N), Hydrogen (H), Carbon (C), and Oxygen (O) 2. Atomic weights: Nitrogen (N) = 14.007, Hydrogen (H) = 1.008, Carbon (C) = 12.011, Oxygen (O) = 15.999 3. Multiply by the number of atoms: (2 × 14.007) + (4 × 1.008) + (1 × 12.011) + (1 × 15.999) 4. Formula weight of (NH2)2CO = 28.014 + 4.032 + 12.011 + 15.999 = 60.056 g/mol
05

(e) Formula weight of Isopentyl acetate (CH3CO2C5H11)

: 1. Identify elements: Hydrogen (H), Carbon (C), and Oxygen (O) 2. Atomic weights: Hydrogen (H) = 1.008, Carbon (C) = 12.011, Oxygen (O) = 15.999 3. Multiply by the number of atoms: (3 × 1.008) + (2 × 12.011) + (5 × 12.011) + (11 × 1.008) + (1 × 15.999) 4. Formula weight of CH3CO2C5H11 = 3.024 + 24.022 + 60.055 + 11.088 + 15.999 = 114.188 g/mol

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Most popular questions from this chapter

Calculate the percentage by mass of the indicated element in the following compounds: (a) carbon in acetylene, \(\mathrm{C}_{2} \mathrm{H}_{2},\) a gas used in welding; (b) hydrogen in ascorbic acid, \(\mathrm{HC}_{6} \mathrm{H}_{7} \mathrm{O}_{6},\) also known as vitamin C; (c) hydrogen in ammonium sulfate, \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}\), a substance used as a nitrogen fertilizer; (d) platinum in \(\mathrm{PtCl}_{2}\left(\mathrm{NH}_{3}\right)_{2},\) a chemotherapy agent called cisplatin; (e) oxygen in the female sex hormone estradiol, \(\mathrm{C}_{18} \mathrm{H}_{24} \mathrm{O}_{2}\); (f) carbon in capsaicin, \(\mathrm{C}_{18} \mathrm{H}_{27} \mathrm{NO}_{3},\) the compound that gives the hot taste to chili peppers.

Without doing any detailed calculations (but using a periodic table to give atomic weights), rank the following samples in order of increasing number of atoms: \(0.50 \mathrm{~mol} \mathrm{H}_{2} \mathrm{O}\), \(23 \mathrm{~g} \mathrm{Na}, 6.0 \times 10^{23} \mathrm{~N}_{2}\) molecules.

The complete combustion of octane, \(\mathrm{C}_{8} \mathrm{H}_{18}\), the main component of gasoline, proceeds as follows: \(2 \mathrm{C}_{8} \mathrm{H}_{18}(l)+25 \mathrm{O}_{2}(g) \longrightarrow 16 \mathrm{CO}_{2}(g)+18 \mathrm{H}_{2} \mathrm{O}(g)\) (a) How many moles of \(\mathrm{O}_{2}\) are needed to burn \(1.50 \mathrm{~mol}\) of \(\mathrm{C}_{8} \mathrm{H}_{18} ?\) (b) How many grams of \(\mathrm{O}_{2}\) are needed to burn \(10.0 \mathrm{~g}\) of \(\mathrm{C}_{8} \mathrm{H}_{18} ?\) (c) Octane has a density of \(0.692 \mathrm{~g} / \mathrm{mL}\) at \(20^{\circ} \mathrm{C}\). How many grams of \(\mathrm{O}_{2}\) are required to burn \(15.0 \mathrm{gal}\) of \(\mathrm{C}_{8} \mathrm{H}_{18}\) (the capacity of an average fuel tank)? (d) How many grams of \(\mathrm{CO}_{2}\) are produced when 15.0 gal of \(\mathrm{C}_{8} \mathrm{H}_{18}\) are combusted?

At least \(25 \mu \mathrm{g}\) of tetrahydrocannabinol \((\mathrm{THC}),\) the active ingredient in marijuana, is required to produce intoxication. The molecular formula of \(\mathrm{THC}\) is \(\mathrm{C}_{21} \mathrm{H}_{30} \mathrm{O}_{2}\). How many moles of THC does this 25 \mug represent? How many molecules? (b) Caffeine, a stimulant found in coffee, contains \(49.5 \% \mathrm{C}\), \(5.15 \% \mathrm{H}, 28.9 \% \mathrm{~N},\) and \(16.5 \% \mathrm{O}\) by mass and has a molar mass of \(195 \mathrm{~g} / \mathrm{mol}\). (c) Monosodium glutamate (MSG), a flavor enhancer in certain foods, contains \(35.51 \% \mathrm{C}, 4.77 \% \mathrm{H}, 37.85 \% \mathrm{O},\) \(8.29 \% \mathrm{~N},\) and \(13.60 \% \mathrm{Na},\) and has a molar mass of \(169 \mathrm{~g} / \mathrm{mol}\)

At least \(25 \mu \mathrm{g}\) of tetrahydrocannabinol (THC), the active ingredient in marijuana, is required to produce intoxication. The molecular formula of THC is \(\mathrm{C}_{21} \mathrm{H}_{30} \mathrm{O}_{2}\). How many moles of THC does this \(25 \mu \mathrm{g}\) represent? How many molecules?
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