0.509g sample pure platinumetal was reacted with hcl to firm o.889g of platinum and chlorine. what is the percent by mass of platinum

Platinum plus chlorine equals 0.889 grams whereas the platinum alone is 0.509grams so 0.509/0.889grams = 57%  of the mass of the platinum plus chlorine. The chlorine would be 0.889-0.509=0.38 grams. The chlorine would make up about 42.7% of the total mass in grams.

Ch4 is nonpolar and insoluble in water. since all of the hydrogen atoms are evenly spread around the carbon atom even through the c h bond is polar all the poles cancel each other out.