2 Chemistry Questions. Help?
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<u>Answer:</u> The mass percent of calcium in milk is 0.107 %
<u>Explanation:</u>
To calculate the number of moles, we use the equation:
.....(1)
Given mass of calcium oxalate = 0.429 g
Molar mass of calcium oxalate = 128.1 g/mol
Putting values in equation 1, we get:
The given chemical equation follows:
Sodium oxalate is present in excess. So, it is considered as an excess reagent. And, calcium ion is a limiting reagent because it limits the formation of product.
By Stoichiometry of the reaction:
1 mole of calcium oxalate is produced from 1 mole of calcium ion
So, 0.0033 moles of calcium oxalate is produced from = of calcium ions
- Now, calculating the mass of calcium ions by using equation 1, we get:
Moles of calcium ions = 0.0033 moles
Molar mass of calcium ions = 40 g/mol
Putting values in equation 1, we get:
- To calculate the mass percentage of calcium ions in milk, we use the equation:
Mass of milk = 125 g
Mass of calcium ions = 0.132 g
Putting values in above equation, we get:
Hence, the mass percent of calcium in milk is 0.107 %
Answer:
0.15g
Explanation:
Given parameters:
Number of molecules of water = 1.2 x 10²¹ molecules
Unknown:
Mass of SnO₂ = ?
Solution:
To solve this problem, we have to work from the known to the unknown specie;
SnO₂ + 2H₂ → Sn + 2H₂O
Ensure that the equation given is balanced;
Now,
the known species is water;
6.02 x 10²³ molecules of water = 1 mole
1.2 x 10²¹ molecules of water = = 0.2 x 10⁻²moles
Number of moles of water = 0.002moles
From the balanced chemical equation:
2 mole of water is produced from 1 mole of SnO₂
0.002 moles of water will be produced from = 0.001moles
To find the mass;
Mass = number of moles x molar mass
Molar mass of SnO₂ = 118.7 + 2(16) = 150.7g/mol
Mass = 0.001 x 150.7 = 0.15g