Answer:
a) Limiting: sulfur. Excess: aluminium.
b) 1.56g Al₂S₃.
c) 0.72g Al
Explanation:
Hello,
In this case, the initial mass of both aluminium and sulfur are missing, therefore, one could assume they are 1.00 g for each one. Thus, by considering the undergoing chemical reaction turns out:

a) Thus, considering the assumed mass (which could be changed based on the one you are given), the limiting reagent is identified as shown below:

Thereby, since there 1.00g of aluminium will consume 0.0554 mol of sulfur but there are just 0.0156 mol available, the limiting reagent is sulfur and the excess reagent is aluminium.
b) By stoichiometry, the produced grams of aluminium sulfide are:

c) The leftover is computed as follows:

NOTE: Remember I assumed the quantities, they could change based on those you are given, so the results might be different, but the procedure is quite the same.
Best regards.
Answer:
4.02g of Na2CO3⸱2H2O must be added completing the volume of the solution to 100mL
Explanation:
A 3%(w/v) solution contains 3g of solute (In this case, Na2CO3) in 100mL of solution.
Assuming we require 100mL of solution we must add 3g of Na2CO3. The reactant that is available is its dihydrate, with molar mass:
106g/mol + 2*MW H2O
106g/mol + 2*18g/mol = 142g/mol
That means the mass of Na2CO3.2H2O that must be added to prepare the solution is:
3g Na2CO3 * (142g/mol Na2CO3.2H2O / 106g/mol Na2CO3) =
<h3>4.02g of Na2CO3⸱2H2O must be added completing the volume of the solution to 100mL</h3>
Fossil Fuels Account for Lowest Share of U.S. Energy Consumption in More than a Century. Fossil fuels supplied about 80 percent of the energy consumed in the United States in 2017, the lowest share since 1902, according to a new report from the U.S. Department of Energy.
P = 2.00 atm = 2026.50hPa
T = 27°C = 300K
m = 14.0g |
Mr = 28g/mol | n = m/M = 14g/28g/mol = 0,5mol
R = 83.1 [hPa*L]/[mol*K]
pV = nRT
nRT 0,5mol * 83.1[hPa*L]/[mol*K] * 300K
V = ---------- = ----------------------------------------------------------- = <u>6.15L</u>
p 2026.5hPa
Answer B.