6.72 g of zinc was placed in 0.1L of of 1.5M hydrochloric acid. After reaction stops, how much zinc is left

I got about 3.5 grams, but I don't know if that's right. If someone could walk we though the question I'd be forever grateful.

No, not quite.

Step 1: A balanced equation. I don't think your equation was balanced that's why you got about 3.5

Zn + 2HCl ------------------> ZnCl2 + H2

Step 2: Calculate how many moles there are in 0.1 L of a 1.5M HCl solution.

n = Conc x Vol 1.5 mol/L x 0.1 L = 0.15 mol

Step 3: Now go back to the equation. Notice that you only use 1/2 the moles of Zn as there is moles of HCl? mol Zn = 1, mol HCl = 2?

So we know we have 0.15 mol of HCl so only 1/2 x 0.15 mol of Zn will be used
1/2 x 0.15 = 0.075 mol of Zn

Step 4. Change mol of Zn into mass. mass = mol x Molar Mass

mass = 0.075 mol x 65.38 g/mol = 4.90 g

Step 5: subtract the beginning mass of Zn from the mass used in the reaction to find what's left.

6.72 g - 4.90 g = 1.81 g left.

OK?