Practice Stoichiometry PDF
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Uploaded by HearteningLagoon2119
Balamand University
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This document contains a practice set of chemistry questions on stoichiometry, atomic theory, covering topics such as percentages of elements, empirical formula, isotopes and molecular formula. The questions are aimed at secondary school level.
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Stoichiometry- Atomic Theory 1- a) Calculate the percentage of H in NH4C2H3O2 b) What weight of silver is present in 3.45g of Ag2S c) The arsenic oxide content of an agriculture insecticide was reported as 28% As2O5. What is the percentage of arsenic in this preparation? d) How many atoms of hyd...
Stoichiometry- Atomic Theory 1- a) Calculate the percentage of H in NH4C2H3O2 b) What weight of silver is present in 3.45g of Ag2S c) The arsenic oxide content of an agriculture insecticide was reported as 28% As2O5. What is the percentage of arsenic in this preparation? d) How many atoms of hydrogen are there in 25 g of NH4Cl ? 2- A compound gave on analysis the following percent composition: K =26.57% Cr =35.36% O =38.07% What is the empirical formula of the compound? 3- Calculate the empirical formula of the compound formed when 7.3 g of iron powder reacts completely with 6.3 g of sulfur powder. 4- The element Rhenium (Re) has two naturally occurring isotopes: 185 Re and 187Re ,with an average atomic mass of 186.207 amu. Rhenium is 62.60% 187Re and the atomic mass of 187Re is 186.956 amu. Calculate the mass of 185Re. 5- An alcane consists of 82.66% C and 17.34% of the other element. It has a molecular weight of 58.1 amu. Determine its molecular formula. 6- When 20g of lithium reacts with 30g of oxygen, calculate the number of grams of Li2O formed. 7- Calculate the mass of Ba(ClO3)2 formed from 0.1 L of a 3M HClO3 solution plus an excess of Ba(OH)2. 8- A 15 g sample of an unstable hydrate salt Na2SO4.xH2O was found to contain 7.05g of water. Determine the empirical formula of this salt. 9- A 5g sample of a natural gas, consisting of methane CH4 and ethylene C2H4, was burned in excess oxygen yielding 14.5g of CO2 and some H2O as products. What percent of the sample was ethylene? 10- To account for nitrogen’s atomic weight of 14.0067 amu , what must be the ratio of 15 N to 14N atoms in natural nitrogen. 11- Calculate the number of moles of Cl- ions in 1.75 liters of 1x10-3 M AlCl3 12- A sample of a pure metal M weighing 1.35 g was converted into 1.88g of pure MO. If the atomic weight of oxygen is 16, what is the atomic weight of the metal?
