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Chapter 3: Problem 49

A compound whose empirical formula is \(X F_{3}\) consists of 65\(\%\) F by mass. What is the atomic mass of \(X ?\)

Short Answer

Expert verified
The atomic mass of element X in the compound \(XF_3\) is approximately 30.7 g/mol.

Step by step solution

01

Obtain molar mass of F

Find the molar mass of an F atom which is approximately 19 g/mol.
02

Assume the mass of the XF3 compound

Assume 100 grams of the compound XF3. This way, we can use mass percentage directly without the need for calculations.
03

Calculate the mass of F in the compound

Given that the compound is 65% F by mass, calculate the mass of F in the 100 grams of XF3 compound: Mass of F = 65% * 100 grams = 65 grams
04

Find moles of F in the compound

Divide the mass of F by its molar mass to find the moles of F in the compound: Moles of F = Mass of F / Molar mass of F = 65 grams / 19 g/mol ≈ 3.42 moles
05

Calculate moles of X in the compound

Since each molecule of XF3 contains 3 F atoms, divide the moles of F by 3 to obtain the moles of X: Moles of X = Moles of F / 3 ≈ 3.42 moles / 3 ≈ 1.14 moles
06

Calculate the mass of X in the compound

Subtract the mass of F from the assumed total mass of 100 grams to find the mass of X: Mass of X = 100 grams - 65 grams = 35 grams
07

Calculate the atomic mass of X

Divide the mass of X by the moles of X to find the atomic mass of X: Atomic mass of X = Mass of X / Moles of X = 35 grams / 1.14 moles ≈ 30.7 g/mol The atomic mass of element X is approximately 30.7 g/mol.

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Most popular questions from this chapter

One of the most bizarre reactions in chemistry is called the Ugi reaction: $$ \begin{array}{l}{\mathrm{R}_{1} \mathrm{C}(=\mathrm{O}) \mathrm{R}_{2}+\mathrm{R}_{3}-\mathrm{NH}_{2}+\mathrm{R}_{4} \mathrm{COOH}+\mathrm{R}_{5} \mathrm{NC} \rightarrow} \\ {\mathrm{R}_{4} \mathrm{C}(=\mathrm{O}) \mathrm{N}\left(\mathrm{R}_{3}\right) \mathrm{C}\left(\mathrm{R}_{1} \mathrm{R}_{2}\right) \mathrm{C}=\mathrm{ONHR}_{5}+\mathrm{H}_{2} \mathrm{O}}\end{array} $$ (a) Write out the balanced chemical equation for the Ugi reaction, for the case where \(R=C H_{3} C H_{2} C H_{2} C H_{2} C H_{2} C H_{2}-\) (this is called the hexyl group) for all compounds. (b) What mass of the "hexyl Ugi product" would you form if 435.0 \(\mathrm{mg}\) of \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\) was the limiting reactant?

(a) What is the mass, in grams, of 1.223 mol of iron( III) sulfate? (b) How many moles of ammonium ions are in 6.955 g of ammonium carbonate? (c) What is the mass, in grams, of \(1.50 \times 10^{21}\) molecules of aspirin, \(\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4} ?\) (d) What is the molar mass of diazepam (Valium') if 0.05570 mol has a mass of 15.86 \(\mathrm{g} ?\)

The fizz produced when an Alka-Seltzer tablet is dissolved in water is due to the reaction between sodium bicarbonate \(\left(\mathrm{NaHCO}_{3}\right)\) and citric acid \(\left(\mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}\right) :\) $$ \begin{aligned} 3 \mathrm{NaHCO}_{3}(a q)+\mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}(a q) & \longrightarrow \\ & 3 \mathrm{CO}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(l)+\mathrm{Na}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}(a q) \end{aligned} $$ In a certain experiment 1.00 g of sodium bicarbonate and 1.00 g of citric acid are allowed to react. (a) Which is the limiting reactant? (b) How many grams of carbon dioxide form? (c) How many grams of the excess reactant remain after the limiting reactant is completely consumed?

What is the mass, in kilograms, of an Avogadro's number of people, if the average mass of a person is 160 \(\mathrm{lb}\) ? How does this compare with the mass of Earth, \(5.98 \times 10^{24} \mathrm{kg}\) ?

A piece of aluminum foil 1.00 \(\mathrm{cm}^{2}\) and 0.550 -mm thick is allowed to react with bromine to form aluminum bromide. (a) How many moles of aluminum were used? (The density of aluminum is 2.699 \(\mathrm{g} / \mathrm{cm}^{3} .\) ) (b) How many grams of aluminum bromide form, assuming the aluminum reacts completely?
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