Question

1.00g of a metallic element reacts completely with 300cm3 of oxygen at 298K and 1 atm pressure to form an oxide which contains O2– ions. The volume of one mole of gas at this temperature and pressure is 24.0dm3

Answer 1

Answer:

The metal is most likely calcium which has a molar mass of 40.078 g

Note: The question is incomplete. The complete question is given below:

1.00g of a metallic element reacts completely with 300cm3 of oxygen at 298K and 1 atm pressure to form an oxide which contains O2– ions. The volume of one mole of gas at this temperature and pressure is 24.0dm3 .

What could be the identity of the metal?

A calcium B magnesium C potassium D sodium

Explanation:

Number of moles of the oxygen gas reacted is first determined:

Volume of oxygen gas = 300 cm³ = 0.30 dm³

1 mole of a gas occupies 24.0 dm³ at this temperature and pressure

Number of moles of oxygen gas that will occupy 0.30 dm³ = 0.3/24 = 0.125 moles

Let M be represent the metallic element. The equation of the reaction will be:

2M + O₂ ----> 2MO

From the equation of reaction;

2 moles of the metal reacts with 1 mole of oxygen gas

2 * 0.125 moles of the metal will react with 300 cm³ of oxygen  = 0.025 moles

Since the mass of the metal that reacted with oxygen is 1.0 g, therefore, 1.0 g of the metal = 0.025 moles

mass of 1 mole of the metal = 1 /0.025 = 40.0 g

Therefore, the metal is most likely calcium which has a molar mass of 40.078 g