Answer:
The molarity is 0,35M
Explanation:
The molartity is moles of compound in 1 liter of solution :
20 L----------7moles compound
1 L..-----------x= (1L x7 moles compound )/20L= 0,35 moles compound--> 0,35M
Mass of oxygen : 54 g
<h3>Further explanation
</h3>
Conservation of mass applies to a closed system, where the masses before and after the reaction are the same
Reaction
mass before reaction = mass after reaction
mass C + mass O₂= mass CO₂
The mass of MgO needed to produce 4.8 tonnes of Mg is
8 tonnes or 2,000 Kg or 2,000 ,000 g
calculation
Si + 2 MgO = SiO2 +2 Mg
step 1 :find the moles of Mg
moles = mass/molar mass
mass = 4.8 tonnes = 480,000 g
molar mass = 24 g/mol
moles is therefore = 480,000 g/24g/mol = 200,000 moles
then by use of mole ratio between MgO to Mg which is 1:1 therefore the moles of MgO is also = 200,000 moles
mass of MgO = moles of MgO x molar mass of MgO
molar mass of MgO = 24 + 16 =40 g/mol
therefore the mass = 200,000 moles x 40 g/mol = 8,000,000 grams or 8,000,000/1000= 8,000 Kg or 8,000/1000 = 8 tonnes