Answer:
a) 35.64 g
b) 16.038 g
c) 0.891 g and 10.692 dm^3
Step-by-step explanation:
First, make the equation:
Na + H2O ---> NaOH + H2 balance it and you will get by making the number of each element the same. you can see there are 3 hydrogens in RHS and 2 in LHS after that Oxygen will get imbalanced balancing it will cause imbalance, and so on so add numbers in front of it and you will reach:
2Na + 2H2O → 2NaOH + H2
a) First we need the moles of Na. We can find that by formula by using:
moles= mass/molar mass
We have the mass but we do not have the molecular mass. To find the molar mass we should use the periodic table. In the periodic table, the atomic mass of Na is 23. To find the molar mass we have to multiply the moles by the atomic mass of all elements present and add it to the number of molecules.
Hence Mr= 23 g/mol ( we need to find the mr for 1 mole hence the name 'molar mass')
Therefore:
moles= 20.5/23= 0.891 mol
Locate the alkali you'll see an ionic compound, NaOH, and almost all OH compounds are alkalies.
Now to find the mass we need to find the moles of the alkali, We can do that by ratio method:
Na : NaOH
2 : 2
0.891 : x
x= 0.891
To find the mass, use the formula:
mass= moles × molar mass
Moles is 0.891 as found earlier.
We have the moles but we do not have the molar mass. To find the molar mass we should use the periodic table. In the periodic table, the atomic mass of Na is 23 O is 16 and H is 1 so OH is 17 (1+16). To find the molar mass we have to multiply the moles by the atomic mass of all elements present and add it to the number of molecules.
1×( 23+17) ( we need to find the mr for 1 mole hence the name 'molar mass')
Molecular mass= 40 g/mol
Therefore:
mass= 0.891 × 40= 35.64 g
b) Repeat the same steps:
1) Ratio:
Na : H2O
2 : 2
0.891 : x=0.891
2) mass= moles × molar mass
mass= 0.891 × (16+2)= 16.038 g
c) Repeat the same steps:
1) ratio:
NaOH : H2
2 : 1
0.891 : x
x= 0.891/2= 0.4455 mol
2) mass= moles × molar mass
mass= 0.4455 × 2
mass= 0.891 g
3) To find the volume use the formula:
volume= mol × molar volume (constant at 24 dm^3/ mol)
v= 0.4455 × 24= 10.692 dm^3