Question

78.1 moles li₂so4 = 2 g 6) 1.0 moles bf₃ = 28 7) 34 g li(oh)= ? moles 8) 0.56 moles mg(no₃)2 = 28 9) 87 g li₂so4= ? moles

Answer 1

Answer:

Calculating moles from grams involves dividing the mass of the substance by its molar mass. For example, to find the number of moles in 87 g of Li2SO4, divide by the molar mass of Li2SO4 (109.94 g/mol), resulting in 0.791 mol Li2SO4. To convert 34 g of LiOH to moles, divide by the molar mass of LiOH (23.95 g/mol), giving approximately 1.42 moles of LiOH.

Explanation:

The student's question involves converting between grams and moles of different chemical compounds, which is a fundamental concept in chemistry, specifically in stoichiometry. To convert from grams to moles, the molar mass of the compound needs to be used. Conversely, to convert from moles to grams, the molar mass is multiplied by the number of moles.

For example, to find the number of moles in 87 g of Li2SO4, one would divide the mass (87 g) by the molar mass of Li2SO4 (which is 109.94 g/mol, not provided in the provided information but can be calculated from atomic masses of lithium, sulfur, and oxygen). The number of moles of Li2SO4 would be 0.791 mol Li2SO4.

Calculating Moles from Grams:

Below are the steps for calculating the moles of lithium hydroxide from grams:

Identify the molar mass of LiOH (which is approximately 23.95 g/mol).

Divide the given mass (34 g) by the molar mass of LiOH to find the number of moles.

The calculation would yield approximately 1.42 moles of LiOH.