Mg (s) + 2 H20 (l) --> H2 (g) + Mg (OH)2 (aq)?

Question

if 3.6 grams of of magnesium is used in the above reaction determine the mass of water needed for the reaction give detail explaining how u know how to do this so i can do it myself

Answer 1

First find the number of moles of magnesium, so you know how many moles of water were used:

13.6 g Mg | 1 mole/ 24.3 g | = 0.56 moles Mg

The reaction says that for every mole of magnesium used, 2 moles of water are used (there's an implied 1 infront of the Mg, and a 2 in front of the H20). That means if you used 0.56 moles of Mg, you would use 2*0.56 = 1.12 moles of H2O.
The mass of a mole of water can be found by adding the masses of the constituent atoms:

2 mole of hydrogen atoms = 2.016 g
1 moles of oxygen atoms = 16.0 g
──► 1 mole of H2O molecules = 18.016 g

Now you can find the mass of 1.12 moles of H2O:

1.12 moles H2O | 18.016 g / mole | = 20.16 g H2O

Answer 2

find out how many moles 306 g of Mg is.
3.6 X 1mol =.14808
24.31

muliply that number by 2 because its gonna be your new ratio. (.2961)

multiply that by 18 because thats how many grams of water are in 1 mol
=5.33 grams


Check my math too! Its been a long time since ive done problems like that.

Answer 3

1.Mass of reactant
2.Moles of reactant over molecular wt of reactant
3.Mole ratio from problem
4.Molecular wt of H2O over moles of H2O

1: (3.6 g Mg) / 1
2: (24.31 g Mg) / (1 mol Mg)
3: (2 mol H2O) / (1 mol Mg)
4: (18 g H2O) / (1 mol H2O)

*Write it all out in a line with the first numbers on top and the second numbers on the bottom then multiply the top numbers and divide by the bottom numbers.

*After canceling out terms it leaves you with g of H2O = 5.33

Answer 4

In the reaction, the mole ratio of Mg: H2O: H2 : Mg(OH)2 is 1:2:1:1.
so first, get the # of moles of magnesium...we can use 24g/mol as the molar mass of Mg because there are two significant digits. We can interchange 24g/mol to mol/24g because the are both equal to 1.
3.6g x mol/24g= 0.15mol
We should use the mole ratio of Mg: H2O which is 1:2,therefore, if there is 0.15mol of Mg, there is 0.30mol of H2O...
the molar mass of H2O is
H=2x1.0=2.0 +
O=1x16=16
--------= 18g/mol
Because there are two atoms of hydrogen in H2O, 2 is multiplied with the atomic mass of H which is 1.0 and 1 is multiplied with the atomic mass of O because there are one atom of oxygen in H2O...
then calculate the mass of H2O needed,
0.30mol x 18g/mol= 5.4g of H2O
there, you got the answer of 5.4g... did you get it?
Hope you did...

Answer 5

hmmm something about how many Moles in a gramme.

Think you need to use Avagadro's number.

If you've got Avagadro's number give him a ring and ask him how much water to use.

Answer 6

Use the required amount of water to make coffee instead,your gonna be up all night working that one out

Answer 7

You need about 350 tons. There might be some left over.

Answer 8

Show off
Ask Elvis

Answer 9

12 frogs squared (sorry not a clue)

Answer 10

listen in class and maybe you will be able to do your own homework.