Question

what mass of O2 will react with 24 g of Mg to produce MgO,,

Answer 1

first and most important, is you need a balanced reaction. can you do that?

Answer 2

yup

Answer 3

\[2Mg + O2\rightarrow 2MgO\]

Answer 4

options are 32,16,24,8

Answer 5

good. so, you know the coefficients in front of the formulas tell us a MOLAR ratio, not a MASS ratio, right?

Answer 6

so is it 32

Answer 7

why do you think it's 32?

Answer 8

yup so do i need limiting reactant
calculations

Answer 9

this isn't a limiting reactant problem, since it's the mass of oxygen you're looking for. this is simpler than that

Answer 10

well O2 has 32 mass and on right side it's 2MgO meands

Answer 11

*means that whole O2 is used right???

Answer 12

but you're told 24g of Mg, not MgO. What's special about 24g of Mg? Like something you'd find on the periodic table

Answer 13

i'm only concerned here about the mass of O2 which reacts in this reaction

Answer 14

but to know that, you need to know about the Mg, so what's special about 24g of Mg?

Answer 15

it's the mass of one mole of Mg

Answer 16

exactly

Answer 17

so you have 1 mole of Mg that will be used. What's the ratio of Mg to O2 in the balanced reaction?

Answer 18

2:1

Answer 19

so every time 2 atoms (or moles) of Mg react, only 1 O2 will react.

Answer 20

ohh so it's 16 g of O2 reacting cuz i'm asked to find the mass reacting with 1 mole of Mg and

Answer 21

So from that, if you use 1 mole of Mg, you'll only use ..... HALF a mole of O2

Answer 22

means 16g right????

Answer 23

yes

Answer 24

thanks

Answer 25

can u help me over one more question

Answer 26

@JFraser

Answer 27

sure

Answer 28

1 dm cube of an unknown gas weighs 1.25 g at STP. the possible formula for the gas is

CO2, CO, C2H2 , SO2

Answer 29

you have a volume, a temp, and a pressure. you need to find the molar mass using the ideal gas law.

Answer 30

\[PV = nRT\]so\[n = \frac{PV}{RT}\]find the moles of gas, and divide the mass you're given by the moles that you calculate

Answer 31

yup i have 1atm pressure 1K temp and 1dm cube of volume

Answer 32

temp isn't 1K, STP is 273K

Answer 33

ohh sorry got confused

Answer 34

but i'm not given any mass

Answer 35

yes you are, read the problem

Answer 36

ohh yup and after doing this how can i predict the molecular formula of the gas

Answer 37

each of the gases will have its own molar mass. find the molar mass of each option, and the one that is right is the one that is the closest to your value

Answer 38

thanx again