Question

Расчищайте относительно молекулярной массы веществ и определите массовые доли элементов в веществах 4и 5 1). Mr (Nв2) 2). Mr (PHв3) 2). Mr. (HNOв2) 4). Me (Cacl в2) w (Ca) w. (Cl) 5). Mr(MgCo в3) w (Mg) w (C) w (O)

Answer 1

1) Mr (N2) = 14×2=28
2) Mr (PH3) = 31+1×3=34
3) Mr (HNO2) = 1+14+16×2=47
4) Mr (CaCl2)
w (Ca) - ?
w (Cl) - ?
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Mr (CaCl2) = 40+35,5×2=111
w (Ca) = 40÷111 (пишется через черту дроби)= 3,636 или 63,6%
w (Cl) = 35,5×2÷111= 0,639 или 63,9%

5) Mr (MgCO3)
w (Mg) - ?
w (C) - ?
w (O) - ?
-----------
Mr (MgCO3) = 25+12+16×3= 85

Answer 2

Molecular Mass and Mass Percent Composition of Substances

The molecular mass of a substance is the sum of the atomic masses of all the atoms in a molecule. To determine the mass percent composition of elements in a substance, we need to calculate the mass of each element and then divide it by the total molecular mass of the substance.

Let's calculate the molecular masses and mass percent compositions for the given substances:

1) Mr (N2): - Molecular mass of nitrogen (N) = 14.01 g/mol - Molecular mass of nitrogen gas (N2) = 2 * 14.01 g/mol = 28.02 g/mol - Mass percent composition of nitrogen (N) in nitrogen gas (N2) = (2 * 14.01 g/mol) / 28.02 g/mol * 100% = 100%

2) Mr (PH3): - Molecular mass of phosphorus (P) = 30.97 g/mol - Molecular mass of hydrogen (H) = 1.01 g/mol - Molecular mass of phosphine (PH3) = 30.97 g/mol + 3 * 1.01 g/mol = 33.01 g/mol - Mass percent composition of phosphorus (P) in phosphine (PH3) = (30.97 g/mol / 33.01 g/mol) * 100% = 93.9% - Mass percent composition of hydrogen (H) in phosphine (PH3) = (3 * 1.01 g/mol / 33.01 g/mol) * 100% = 6.1%

3) Mr (HNO2): - Molecular mass of hydrogen (H) = 1.01 g/mol - Molecular mass of nitrogen (N) = 14.01 g/mol - Molecular mass of oxygen (O) = 16.00 g/mol - Molecular mass of nitrous acid (HNO2) = 1.01 g/mol + 14.01 g/mol + 2 * 16.00 g/mol = 47.03 g/mol - Mass percent composition of hydrogen (H) in nitrous acid (HNO2) = (1.01 g/mol / 47.03 g/mol) * 100% = 2.15% - Mass percent composition of nitrogen (N) in nitrous acid (HNO2) = (14.01 g/mol / 47.03 g/mol) * 100% = 29.8% - Mass percent composition of oxygen (O) in nitrous acid (HNO2) = (2 * 16.00 g/mol / 47.03 g/mol) * 100% = 68.1%

4) Me (CaCl2): - Molecular mass of calcium (Ca) = 40.08 g/mol - Molecular mass of chlorine (Cl) = 35.45 g/mol - Molecular mass of calcium chloride (CaCl2) = 40.08 g/mol + 2 * 35.45 g/mol = 110.98 g/mol - Mass percent composition of calcium (Ca) in calcium chloride (CaCl2) = (40.08 g/mol / 110.98 g/mol) * 100% = 36.1% - Mass percent composition of chlorine (Cl) in calcium chloride (CaCl2) = (2 * 35.45 g/mol / 110.98 g/mol) * 100% = 63.9%

5) Mr (MgCO3): - Molecular mass of magnesium (Mg) = 24.31 g/mol - Molecular mass of carbon (C) = 12.01 g/mol - Molecular mass of oxygen (O) = 16.00 g/mol - Molecular mass of magnesium carbonate (MgCO3) = 24.31 g/mol + 12.01 g/mol + 3 * 16.00 g/mol = 84.31 g/mol - Mass percent composition of magnesium (Mg) in magnesium carbonate (MgCO3) = (24.31 g/mol / 84.31 g/mol) * 100% = 28.9% - Mass percent composition of carbon (C) in magnesium carbonate (MgCO3) = (12.01 g/mol / 84.31 g/mol) * 100% = 14.2% - Mass percent composition of oxygen (O) in magnesium carbonate (MgCO3) = (3 * 16.00 g/mol / 84.31 g/mol) * 100% = 56.9%

I hope this helps! Let me know if you have any further questions.