Epsom salts, a strong laxative used in veterinary medicine, is a hydrate, which means that a certain number of water molecules are included in the solid structure. The formula for Epsom salts can be written as MgSO4 # xH2O, where x indicates the number of moles of H2O per mole of MgSO4. When 5.061 g of this hydrate is heated to 250 C, all the water of hydration is lost, leaving 2.472 g of MgSO4. What is the value of x?
The reaction between potassium superoxide, KO2, and CO2, 4 KO2 + 2 CO2¡2K2CO3 + 3 O2 is used as a source of O2 and absorber of CO2 in selfcontained breathing equipment used by rescue workers. (b) How many grams of KO2 are needed to form 7.50 g of O2?


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Key Concepts
Stoichiometry
Molar Mass
Balanced Chemical Equation
Hydrofluoric acid, HF(aq), cannot be stored in glass bottles because compounds called silicates in the glass are attacked by the HF(aq). Sodium silicate (Na2SiO3), for example, reacts as follows: Na2SiO3(s) + 8 HF(aq) → H2SiF6(aq) + 2 NaF(aq) + 3 H2O(l) (a) How many moles of HF are needed to react with 0.300 mol of Na2SiO3? (b) How many grams of NaF form when 0.500 mol of HF reacts with excess Na2SiO3? (c) How many grams of Na2SiO3 can react with 0.800 g of HF?
The reaction between potassium superoxide, KO2, and CO2, 4 KO2 + 2 CO2¡2K2CO3 + 3 O2 is used as a source of O2 and absorber of CO2 in selfcontained breathing equipment used by rescue workers. (a) How many moles of O2 are produced when 0.400 mol of KO2 reacts in this fashion?
Several brands of antacids use Al1OH23 to react with stomach acid, which contains primarily HCl: Al(OH)3(s) + HCl(aq) → AlCl3(aq) + H2O(l) (b) Calculate the number of grams of HCl that can react with 0.500 g of Al(OH)3. (c) Calculate the number of grams of AlCl3 and the number of grams of H2O formed when 0.500 g of Al(OH)3 reacts.
An iron ore sample contains Fe2O3 together with other substances. Reaction of the ore with CO produces iron metal: Fe2O3(s) + CO(g) → Fe(s) + CO2(g) (b) Calculate the number of grams of CO that can react with 0.350 kg of Fe2O3. (c) Calculate the number of grams of Fe and the number of grams of CO2 formed when 0.350 kg of Fe2O3 reacts.
Aluminum sulfide reacts with water to form aluminum hydroxide and hydrogen sulfide. (a) Write the balanced chemical equation for this reaction. (b) How many grams of aluminum hydroxide are obtained from 14.2 g of aluminum sulfide?