It's a hazard symbol for irritant.
1.B
6.D
D because t<span>he mass of one mole (molar mass) of helium gas is </span>4.002602 g/mol. 4.002602 * 5=20.01309. Rounded equals 20. So, the answer is D.20 g.
Answer: a)
: Decomposition
b)
: double displacement
c)
: Synthesis (Combination)
d)
: redox
Explanation:
Decomposition is a type of chemical reaction in which one reactant gives two or more than two products.

A double displacement reaction is one in which exchange of ions take place.

Synthesis reaction is a chemical reaction in which two reactants are combining to form one product.

Redox reaction is a type of chemical reaction in which oxidation and reduction takes place in one single reaction. The oxidation number of one element increases and the oxidation number of other element decreases.

Fe2O3 + 2Al ---> Al2O3 + 2Fe
Mole ratio Fe2O3 : Al = 1:2
No. of moles of Fe2O3 = Mass/RMM = 250 / (55.8 * 2 + 16 * 3) = 1.56641604 moles
No. of moles of Al = 150/27 = 5.555555555 moles.
Mole ratio 1 : 2. 1.56641604 * 2 = 3.13283208 moles of Al, but you have 5.555555555 moles of Al. So Al is in excess. All of it won't react.
So take the Fe2O3 and Fe ratio to calculate the mass of iron metal that can be prepared.
RMM of Fe2O3 / Mass of Fe2O3 = RMM of 2Fe / Mass of Fe 159.6 / 250 = 111.6 / x x = 174.8 g of Fe