You can get up to Plat V from placements on your first placing season.
However, it's unlikely.
Your placements on a new account generally will start you around Gold III on your first placement game, slightly adjusted for how you performed in your Normalss pre first pre-season placement.
Your first 2-3 games of your first placement will more or less decide where you fall.
Depending who are are placed versus in the placements, the first couple games are effectively worth 200-280 MMR each (your first season; subsequent seasons they are only worth about 48). If you lose them, your continuing Placement games will drop in elo rapidly.
In other words, you'll probably start off vs High Gold/Plat V players with poor MMRs for Plat.
After a couple losses, you'll be vs low golds/high silvers.
If you win them, you'll be vs High Golds/Plat V's who have GOOD MMR's for their rank, which means you might have much more difficulty winning.
Games 3-5 of your Placements will then more or less decide whether to keep dropping you, or whether to help you settle into a specific rank.
If you lost your first 2 games of Placements, but win the next 3, you probably will have an MMR around a Gold IV - Gold V for the remainder of your placements.
If you won your first 2, and win the next 3, you probably have an MMR around Gold II - Gold I going into the last 5 games.
If you lost/lost, you're probably sharply dropping and will end up in Silver or Bronze.
If you lost/win, you might recover slightly and be around Silver I
The last 5 games are more or less about maintaining your mmr you set for the first 5 games, which means you might get adjusted 1 rank down or up from where you are by game 5, because the MMR gains/losses around these games generally are minor and might range from 120 points from 5 games to 200 total (whereas the very first games were huge swings per game)
The system's much simpler than what I'm explaining (there's a formula) BUT, the reason it more or less happens this way is:
-The system matches you with what it assumes are like-MMR opponets. Given you start out with no numbers to calculate, it makes assumptions. By putting you in an estimated MMR based off no scores, sometimes it's wrong, and the system rewards people who beat those estimates. If you are beating Plat players as an estimated gold, the system rewards that more than if you were beating same tier Gold (Post placements you will see this kind of reward reflected in how much LP you get for a win; which is generally higher if you're pulling 50%+ win rates than if you have a 48% win rate)
In other words, as you gain more games for the system to calculate on you, your rewards are more appropriate, and in smaller numbers. By about game 5 of your placements, the system generally knows how you are performing.
You can probably place Gold V if you do well in your first few games at least. if you lose 8/10 games, you're probably mid/silver.
10/10 might get you Gold I, UNLESS your very first games were populated with high Plat MMR players, and you beat them, which can lead to a Plat V placement. VERY unlikely and like winning the lottery.