GK
CHEMISTRY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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0.5 moles
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104.1 moles
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2.2 moles
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50 moles
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Detailed explanation-1: -Answer and Explanation: There are 2.2 moles of Li in 15 grams of Li. To convert between grams and moles, molar mass must be used.
Detailed explanation-2: -The numeric value of this constant is 6.022×1023.-Now, we can find the number of moles by the formula of moles that is given mass of the substance divided by the molar mass of the substance.-Hence, we can conclude that there are 17.28×1023 moles in 15 grams of lithium.
Detailed explanation-3: -Why use 12 grams? This is the theoretical atomic mass of the Carbon-12 isotope (6 protons and 6 neutrons). This means that the atomic mass or atomic weight (12 grams) of carbon is equal to exactly 1 mole of carbon. Lithium for instance has an atomic mass of 6.941 grams and this is equal to one mole of lithium.
Detailed explanation-4: -So, How many mols of Li are in 14g of Li. If you look at the periodic table, you’ll see that 1 mol of Li = 6.94g of Li. 1 mol Li / 6.94 g = x mol Li / 14 g of Li; this gives you 2.02 mol of Li.
Detailed explanation-5: -The molar mass of calcium phosphate Ca3(PO4)2 is about 310 g/mol and 2.3*10^-4 mol have a mass of 2.3*10^-4 * 310 = 0.0713 g = 71.3 mg.