8g of hydrogen is burnt in the presence of excess oxygen.the mass of water formed is?
2H2 + O2 ==> 2H2O
mols H2 = grams/molar mass H2 = ?
mols H2 x 1 = mols H2O
grams H2O = mols H2O x molar mass H2O
40g
To find the mass of water formed from the given information, we need to consider the chemical reaction between hydrogen and oxygen.
The balanced chemical equation for the combustion of hydrogen gas (H₂) in the presence of oxygen gas (O₂) to form water (H₂O) is:
2H₂ + O₂ -> 2H₂O
From the balanced equation, we can see that 2 moles of hydrogen gas react with 1 mole of oxygen gas to produce 2 moles of water.
The molar mass of hydrogen (H₂) is 2 g/mol, so if we have 8g of hydrogen gas, it means we have 8/2 = 4 moles of hydrogen gas.
Since the reaction follows a 2:1 ratio between hydrogen and oxygen, it means we need half the number of moles of oxygen for the reaction, which is 4/2 = 2 moles of oxygen.
The molar mass of water (H₂O) is 18 g/mol, so 1 mole of water weighs 18g.
Since 2 moles of water are formed for every 2 moles of hydrogen, we can conclude that 1 mole of hydrogen forms 1 mole of water.
Therefore, 4 moles of hydrogen will form 4 moles of water, which is equivalent to 4 * 18 = 72g of water.
Thus, the mass of water formed when 8g of hydrogen is burnt is 72g.