Please help on a few chem questions.?

Question

1) If a 17.0-g sample of impure nickel metal reacts with excess CO at 0 °C and 1 atm to form 6.25 L of
Ni(CO)4 gas, what is the percent of nickel in the sample?

2) Which molecule contains polar bonds but is nonpolar? Why?
a) SCl2
b) OF2
c) SiCl4
d) NCl3
e) SO2

3)An aqueous solution of glycerol, C3H8O3, is 48% glycerol by mass and has a density of 1.120 g/mL.
Calculate the molality (m) of the glycerol solution.

I just can't figure these ones out. I'd appreciate any help. Thanks.

Answer 1

Problem #1 needs some math. Here is the concept, you do the calculations.

6.24 L of any gas at STP. divide by 22.4 L /mole and you have the moles of gas.

Calculate the percentage of Ni in this compound, multiply by the moles from above and you have mole fraction of Ni.

Now you can calculate the grams of pure Ni, using its molecular mass. Now compare the grams to the 17.0 grams of impure material and you can calculate the % purity.

For question #2 it is SiCl4. It is perfectly symmetrical tetrahedron, therefore it is non-polar.

For #3. Calculate the weighted average required to produce a density of 1.12 g/ml. You know that water is 52% and has a density of 1 g/ml. You know the molecular mass of both compounds.

Now that you have moles of each, you have the grams of each and you can calculate the molaltiy.

Now that you know