Question

ПОМОГИТЕ! Для наложения гипсовой повязки хирург использовал 290 г алебастра. Какое количество вещества воды было израсходовано в результате превращения алебастра в гипс? Какова масса гипса?

Answer 1

Алебастр разводится в пропорции 1:2. На 2 части гипса, 1 часть воды. Тогда на 290г. гипса потребовалось (290/2) = 145, 145г. воды.

Answer 2

Calculation of Water Used and Mass of Gypsum

To calculate the amount of water used and the mass of gypsum formed, we need to know the stoichiometry of the reaction between plaster of Paris (calcium sulfate hemihydrate) and water. The balanced equation for this reaction is as follows:

CaSO4 · 1/2H2O + 3/2H2O → CaSO4 · 2H2O

According to the equation, one mole of calcium sulfate hemihydrate reacts with 1.5 moles of water to form two moles of gypsum.

Given that the surgeon used 290 g of plaster of Paris (calcium sulfate hemihydrate), we can calculate the amount of gypsum formed and the amount of water used.

1. Calculation of Water Used: - The molar mass of calcium sulfate hemihydrate (plaster of Paris) is 145.15 g/mol. - The molar mass of water is 18.015 g/mol.

To calculate the moles of calcium sulfate hemihydrate used, we divide the mass by the molar mass:

Moles of calcium sulfate hemihydrate = mass / molar mass = 290 g / 145.15 g/mol = 2 moles

Since the stoichiometry of the reaction is 1.5 moles of water per mole of calcium sulfate hemihydrate, we can calculate the moles of water used:

Moles of water used = 1.5 moles of water per mole of calcium sulfate hemihydrate × 2 moles of calcium sulfate hemihydrate = 3 moles

To calculate the mass of water used, we multiply the moles of water used by the molar mass of water:

Mass of water used = moles of water used × molar mass of water = 3 moles × 18.015 g/mol = 54.045 g

Therefore, the surgeon used approximately 54.045 g of water for the transformation of plaster of Paris into gypsum.

2. Calculation of Mass of Gypsum: - The molar mass of gypsum (calcium sulfate dihydrate) is 172.17 g/mol.

Since the stoichiometry of the reaction is 2 moles of gypsum per mole of calcium sulfate hemihydrate, we can calculate the moles of gypsum formed:

Moles of gypsum formed = 2 moles of gypsum per mole of calcium sulfate hemihydrate × 2 moles of calcium sulfate hemihydrate = 4 moles

To calculate the mass of gypsum formed, we multiply the moles of gypsum formed by the molar mass of gypsum:

Mass of gypsum formed = moles of gypsum formed × molar mass of gypsum = 4 moles × 172.17 g/mol = 688.68 g

Therefore, the mass of gypsum formed is approximately 688.68 g.

Please note that these calculations are based on the stoichiometry of the reaction and assume complete conversion of the calcium sulfate hemihydrate to gypsum. In practice, there may be some losses or variations in the reaction.