PLZZZZZ help..mole concepts problem..plzzzzz.?

Question

1.) 2.4g of Mg burning in oxygen gives 4g of MgO.What is equvalent weight of magnesium

Answer 1

The chemical equation for this reaction is

2Mg + O2 --> 2MgO

Since the molar mass of Mg is 24 g/mol, 2.4g of Mg is approximately 0.1mol. Since the coefficients in front of Mg and MgO are both 2, the number of moles of MgO produced are the same as the number of moles of Mg consumed in the reaction, so there's a 0.1mol yield of MgO. The molar mass of MgO is 40g/mol, and since there is 0.1 mol, 4g of MgO should be yielded. That's what we expect from the question. Since the coefficient in front of O2 is 1, half of the number of moles of Mg are consumed, which is 0.05mol. That's 0.8g of O2.

Answer 2

I believe you have to start with a balance equation.

2 Mg(s)+O_2_(g) -> 2 MgO(s)

Its a reverse limited reactant problem. You are given the amount of MgO that can be produced. So you have 4g of MgO, find the molar mass=40g/mol, so now you can do grams:mole:mole:grams calculations.

4gMgO*(1 mol MgO/40g MgO)*(2 mol Mg/2 mol MgO)*(24g Mg/1mol Mg)=2.4 g Mg

If I understood correctly that should be correct