There should be 836 yards in a package of 16oz of yarn.
About 1.7 to 1.9 ounces. http://www.crochet-world.com/blog/?p=7272
Grams is a measurement of weight and yards is a measurement of length so it is hard to say definitively how many yards in any one package. That said, however, I checked one fingering weight yarn and it said 50g is 1 3/4 ounces. You might like to check several different manufacturers to compare.
You can not determine how many yards from the weight of the skein or cone. 50 grams is 1.75 ounces but it would depend on the exact thickness and type of yarn to know how many yards. The thicker the yarn the less the yards as a rule. Example a 50 gram ball of sport yarn can be anywhere from 110 to 170 yards give or take , but a 50 gram ball of bulky can be anywhere from 30 yards to 60 yards give or take ..
It will depend on the type of yarn. 225 yards of worsted weight yarn is about 100g, but 225 yards of sock weight yarn is about 25g. What is the yarn type?
They can't be compared. A yard is a distance, an ounce is a weight. The length of 2 ounces of yarn would depend upon the thickness of the yarn and the type of material the yarn is made of (lambs wool, acrylic, etc). I have had some luck when substituting a yarn with a replacement that was an equivalent grams per meter (ounces per yard).
4 yards.
it varies by company , type of yarn ( like wool , acrylic, blends, etc) but as a rule it would be around 200 yards up to about 275 yards . at 200 yards you would be figuring safe
It depends very much on the bulk and type of yarn.
Since the regular Red Heart skein is four ounces, the pound package is four skeins for your conversion chart.
Depends on the yarn. There is yarn that is 100% cotton, but cotton/rayon mixes and other mixes are common.
It's very slightly less than 175 yards.
It is hard to say . . . it depends on whether the yarn is fine, bulky, or somewhere in the middle.