4. a) A given inorganic compound contains only silicon (Si) and hydrogen (H). If the mass percentage of Si in this compound is 90.28%, what is the mass percentage of H in this compound? ( Hint: Mass% values of all the elements in a given compound should ultimately add up to what % ? Show work. Include units (the % symbol) and observe proper sig figs. b) What is the empirical formula of the compound in part a) ? Hint: You are going to have to refer to the periodic table to find molar masses of Si and H at some point during this calculation. Slide # 48 in Chapter 3 will be helpful to refer to. At each step, make sure to include at least four decimal places to avoid over- / under-estimating the empirical formula values.

4. a) A given inorganic compound contains only silicon (Si) and hydrogen (H). If the mass percentage of Si in this compound is 90.28%, what is the mass percentage of H in this compound? ( Hint: Mass% values of all the elements in a given compound should ultimately add up to what % ? Show work. Include units (the % symbol) and observe proper sig figs. b) What is the empirical formula of the compound in part a) ? Hint: You are going to have to refer to the periodic table to find molar masses of Si and H at some point during this calculation. Slide # 48 in Chapter 3 will be helpful to refer to. At each step, make sure to include at least four decimal places to avoid over- / under-estimating the empirical formula values.

Chemistry: The Molecular Science

5th Edition

ISBN:9781285199047

Author:John W. Moore, Conrad L. Stanitski

Publisher:John W. Moore, Conrad L. Stanitski

Chapter2: Chemical Compounds

Section: Chapter Questions

Problem 143QRT: The present average concentration (mass percent) of magnesium ions in seawater is 0.13%. A chemistry...

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The present average concentration (mass percent) of magnesium ions in seawater is 0.13%. A chemistry textbook estimates that if 1.00 × 108 tons Mg were taken out of the sea each year, it would take one million years for the Mg concentration to drop to 0.12%. Do sufficient calculations to either verify or refute this statement. Assume that Earth is a sphere with a diameter of 8000 mi, 67% of which is covered by oceans to a depth of 1 mi, and that no Mg is washed back into the oceans at any time.
3.123 Most periodic tables provide molar masses with four or five significant figures for the elements. How accurately would you have to measure the mass of a sample of roughly 100 g to make a calculation of the number of moles of the chemical to have its significant figures limited by the molar mass calculation rather than the mass measurement?
A chemist prepared a compound that she thought had the formula FeI3. When the compound was analyzed, it contained 18.0% Fe and 82.0% I. Calculate the mass percentage composition expected for FeI3 and compare the result with that found in the analysis. Is this the correct formula of the compound?
The active ingredient in some antiperspirants is aluminum chlorohydrate, Al2(OH)5Cl. Analysis of a 2.000-g sample of antiperspirant yields 0.334 g of aluminum. What percent (by mass) of aluminum chlorohydrate is present in the antiperspirant? (Assume that there are no other compounds containing aluminum in the antiperspirant.)
The principal component of mothballs is naphthalene, a compound with a molecular mass of about 130 amu, containing only carbon and hydrogen. A 3.000-mg sample of naphthalene burns to give 10.3 mg of CO2. Determine its empirical and molecular formulas.
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You take 1.00 g of an aspirin tablet (a compound consisting solely of carbon, hydrogen, and oxygen), burn it in air, and collect 2.20 g CO2 and 0.400 g H2O. You know that the molar mass of aspirin is between 170 and 190 g/mol. Reacting 1 mole of salicylic acid with I mole of acetic anhydride (C4H6O3) gives you 1 mole of aspirin and 1 mole of acetic acid (C2H4O2). Use this information to determine the molecular formula of salicylic acid.