There is no hard and fast number that I could give you as an answer. It all depends on what the yarn is made of, what "weight" the yarn is (sock versus bulky, for example). So, as asked, this isn't really an answerable question--there is too much unknown about your yarn to answer with any certainty.
My best suggestion would be to go to the yarn manufacturers website and look there for your answer. Or, go back to where you purchased the yarn, and ask there.
It really depends on the type of yarn (fingering, worsted, bulky/chunky, etc.) For worsted weight yarn, I would bet a 50 g. skein would be about 90-93 yards.
150
Are you knitting or etc. because chrocheting takes up lots of yarn
how many yards are in a skein of cross stitch thread
Another name for a hank of yarn would be a skein of yarn.
The length of yarn in a skein varies greatly with brand, variety, etc. You can determine the length of the yarn by looking on the front of the label, where it is listed along with weight, recommended needle/hook size and dye lot
skein
Approximately 1000. However, brands vary. It should give the measurement on the ball band.
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 ..
Yarn comes in different "gatherings"--ways that it can be sold. Your question mentioned 2 out of the three: ball of yarn and skein of yarn. The third would be a Hank of yarn. A hank is a skein of yarn (which is yarn in a large oblong shape, and tied in a few places around the skein to maintain a bit of control over the yarn staying in that loose shape), which has been twisted around itself to make for a smaller and more controllable yarn, which is easier to pack, and store. A hank also is a bit more manageable than a skein of yarn. A ball of yarn would be wound from a skein or a hank.
Depends on the yarn. There is yarn that is 100% cotton, but cotton/rayon mixes and other mixes are common.
A skein of wool can come in different weights. There is not a specific amount of wool needed in a skein.
A coil of yarn may be called a hank or a skein. Yarn is typically sold in a ball or a skein. A hank is different in that it is a big loop of yarn that is twisted up for easy shipping.
After yarn is spun it is wound into a skein on a niddy-noddy or skein winder. A skein is a coil of yarn wound like a garden hose, with a circumference usually of 1-2 yards. Before it is used for knitting, a skein is placed on a yarn swift which spins freely as the yarn is pulled from it, and the yarn is then wound into a center-pull ball, or cake with a nostapinne or ball winder. Alternately, an unwitting spouse can be used as a substitute swift by placing the skein of yarn over his hands and directing him to slowly move his hands side to side as the yarn is pulled off by the person winding. The back of a chair might also be used as a substitute swift. Commercially prepared yarns already wound into a center-pull tube-less cone are often mistakenly called "skeins" because they resemble skeins that have been twisted for storage and because they lack the cardboard core typical to cones.