Expert Chemistry Tutoring

MS1.

- The mole is the amount of substance containing 6.022 x 10^23 specified particles (1)

- Unit is mol (1)

MS2.

- Molar mass is the mass of one mole of a substance (1)

- Relative formula mass is the ratio of the mass of a molecule or formula unit of a substance to 1/12th of the mass of a carbon-12 atom (1)

- Since the mole contains 6.022 x 10^23 particles, which is the same as the ratio in the definition of relative formula mass, they are numerically equal (1)

MS3.

- Calculate molar mass: 23.0 + 35.5 = 58.5 g/mol (1)

- Convert mass to moles: 50.0 g / 58.5 g/mol = 0.855 mol (1)

MS4.

- Empirical formula gives the simplest whole number ratio of atoms in a compound (1)

- Molecular formula gives the actual number of atoms in a molecule of a compound (1)

MS5.

- Mole ratio: 1 mole of hydrogen reacts with 1 mole of chlorine to produce 2 moles of hydrogen chloride (1)

MS6.

- Mole ratio: 1 mole of methane produces 2 moles of water (1)

- Calculate moles of water: 2.5 moles CH4 x 2 moles H2O/1 mole CH4 = 5.0 moles H2O (1)

MS7.

- Limiting reactant is the reactant that is entirely consumed in a chemical reaction (1)

- It limits the amount of product that can be formed (1)

MS8.

- Mole ratio: 1 mole of Mg reacts with 2 moles of HCl (1)

- Comparison: 0.50 moles Mg / 1 = 0.25; 1.00 moles HCl / 2 = 0.50

- Therefore, Mg is the limiting reactant because it runs out first (1)

MS9.

- Calculate moles of NaOH: 25.0 cm³ x 0.200 mol/dm³ / 1000 = 0.00500 mol (1)

- Mole ratio: 1 mole of NaOH produces 1 mole of NaCl (1)

- Calculate mass of NaCl: 0.00500 mol x (23.0 + 35.5) g/mol = 0.298 g (1)

MS10.

- Charles' Law: Volume of a gas is directly proportional to temperature at constant pressure (1)

- Boyle's Law: Volume of a gas is inversely proportional to pressure at constant temperature (1)