A 7.7 g sample of an unknown alkaline earth metal X in group...

A 7.7 g sample of an unknown alkaline earth metal X in group II burns completely in oxygen to form a single product. During the reaction 5. 068 g of oxygen is consumed. What is the molar mass of the metal oxide compound? Start by writing the balanced reaction. (A) 25.01 g/mole (B) 40. 31 g/mole (C) 56.08 g/mole (D) 103. 6 g/mole (E) 153. 3 g/mole

Transcript

0:00 Hello.

00:02 So here we've been given the mass of the metal with 0 .356 grams.

00:19 Right? we also have the mass of the metal oxide of 0 .452 grams.

00:35 So what we need to do first is to calculate the percentage of metal in the sample.

00:42 So the percentage of the metal in the sample is going to be the mass of the metal grams over the mass of the oxide, which is the 4, 52 grams times 100.

01:16 So that's going to give us 78 .76%.

01:25 So we're going to say that we're going to let m be the atomic mass of the metal.

01:31 Okay so the outside of the metal oxide was given us this i mean we can use any value let's just say x you know let's say let x be equal to the atomic mass or the motor mass to make mass over the metal in the oxide okay so you want to find a percentage of that so it's going to be the atomic mass of x over the atomic mass of x over the atomic mass of the whole, you know, oxide times 100.

02:21 We want to find a percentage of that as well.

02:24 That's going to be x.

02:26 Now, m2, you don't know what m is.

02:32 That's what we're trying to find.

02:33 So m is going to be x, right? and then we have oxygen.

02:38 The amount of oxygen is 16, and we have two of that.

02:41 So that's going to be 32 times 100%.

02:47 So what we have this percentage right here is what we got here.

02:56 So we can equate this to 78 .76.

03:06 We can do that...

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