2. A 0.45g sample of mineral ore is analyzed for chromium and found to contain 0.560mg Cr2O3. Express the concentration of Cr2O3 in the sample as:
(a) Percent (%)
(b) Parts per thousand (ppt)
(c) Parts per million (ppm)
(d) Parts per billion (ppb)​

Explanation: I don't know

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explanation:

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g