Chemistry question here.?

Question

1)Vitamin B12 is 4.34% Co.If there is only one atom of Co per molecule of vitamin,what is the molar mass of Vitamin B12?
2)How many grams of H2 can be obtained from the electrolysis of 10.0g of H2O?
3)How many grams of CuO can be made from a piece of copper wire weighing 0.2134g?

Answer 1

This looks like three questions.

1) Vitamin B12 is 4.34% Co.If there is only one atom of Co per molecule of vitamin,what is the molar mass of Vitamin B12?

If 4.34% of B12 is Cobalt, 4.34% of the mass of each molecule is Co. Cobalt has an atomic mass of 58.93 g/mol. Divide this by the percentage (0.0434) to get the molar mass of Vitamin B12.

2)How many grams of H2 can be obtained from the electrolysis of 10.0g of H2O?

2 H2O (l) --> 2 H2 (g) + O2 (g)

One mole of water gives one mole of H2 gas. The molecular mass of water is 18.0 g/mol. The number of moles of water would be:

10.0 g / 18.0 g/mol = moles of water

This is also the moles of H2 produced, so multiple this number by the molecular mass of the Hydrogen (2.016 g/mol) to get the number of grams of H2 produced.

3)How many grams of CuO can be made from a piece of copper wire weighing 0.2134g?

2 Cu + O2 --> 2 CuO

Two moles of Copper gives two moles of CuO (or one gives one).

The number of moles of Cu is

0.2134 g / 63.55 g/mol = number of moles of Copper used.

The mass of the Copper (II) oxide would be that number of moles times the formula mass of the CuO (which is 79.545 g/mol)

Answer 2

All of these can be answered by correctly predicting the reaction taking place, balancing it, and applying stoichiometry correctly to that balanced equation.

Which part(s) do you need help with? I don't think anyone is goign to glibly do your homework for you.....