Q1: How much O₂ can be obtained from 90 kg of water ?

ANS:B - 80 kg

To determine how much 𝑂2O2​ can be obtained from 90 kg of water, we need to consider the process of electrolysis. In electrolysis, water (𝐻2𝑂H2​O) can be decomposed into its constituent elements, hydrogen (𝐻2H2​) and oxygen (𝑂2O2​), through the application of an electric current. The chemical equation for the electrolysis of water is: 2𝐻2𝑂→2𝐻2+𝑂22H2​O→2H2​+O2​ From this equation, we can see that for every 2 moles of water decomposed, 1 mole of oxygen is produced. The molar mass of water (𝐻2𝑂H2​O) is approximately 18 g/mol18g/mol. Therefore, 90 kg of water is equal to: 90 kg×1000 gkg×1 mol18 g=5000 mol90kg×kg1000g​×18g1mol​=5000mol Since 2 moles of water produce 1 mole of oxygen, the number of moles of oxygen produced is half of the number of moles of water decomposed: moles of 𝑂2=5000 mol2=2500 molmoles of O2​=25000mol​=2500mol Now, we need to convert the number of moles of 𝑂2O2​ to kilograms using its molar mass. The molar mass of 𝑂2O2​ is approximately 32 g/mol32g/mol. Therefore: mass of 𝑂2=2500 mol×32 g/mol×1 kg1000 g=80 kgmass of O2​=2500mol×32g/mol×1000g1kg​=80kg So, 90 kg of water can produce 80 kg80kg of 𝑂2O2​. Therefore, the correct answer is: 80 kg80kg​