Answer:
O B. Convert the 10 g of NaCl to moles of NaCl.
Explanation:
The formula for finding the molality is m=moles of solute/kg of solvent. The solute for this question is NaCl and the solvent is water.
(10g NaCl)(1 mol NaCl/58.44g NaCl)=0.1711 mol NaCl
58.44 is the molar mass of NaCl
m=0.1711 mol NaCl/2 kg H2O
m=0.085557837
Answer:
There are often not more than one or two independent variables tested in an experiment.
Hydrogen gas and oxygen gas react to form liquid water according to the following equation:
2H₂ + O₂ → 2H₂O
a. Converting our given masses of each gas to moles, we have:
(25 g H2)/(2 × 1.008 g/mol) = 12.4 mol H2; and
(25 g O2)/(2 × 15.999 g/mol) = 0.781 mol O2.
From the equation, two moles of H2 react with every one mole of O2. To fully react with 12.4 moles of H2, as we have here, one would need 6.2 moles of O2, which is far more than what we're actually given. Thus, the oxygen is our limiting reactant, and as such it will be the first reactant to run out.
b. Since O2 is our limiting reactant, we use it for determining how much product, in this case, H2O, is produced. From the equation, there is a 1:1 molar ratio between O2 and H2O. Thus, the number of moles of H2O produced will be the same as the number of moles of O2 that react: 0.781 moles of H2O. The mass of water produced would be (0.781 mol H2O)(18.015 g/mol) ≈ 14 grams of water (the answer is given to two significant figures).
c. Since the hydrogen reacts with the oxygen in a 2:1 ratio, twice the number of moles of oxygen in hydrogen is consumed: 0.781 mol O2 × 2 = 1.562 mol H2. Since we began with 12.4 moles of H2, the remaining amount of excess H2 would be 12.4 - 1.562 = 10.838 mol H2. The mass of the excess hydrogen reactant would thus be (10.838 mol H2)(2 × 1.008 g/mol) ≈ 22 grams of hydrogen gas (the answer is given to two significant figures).
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Answer:
b. mercury
Explanation:
Fishes and some other sea foods are are known to concentrate mercury in their bodies. Consumption of these products gradually accumulate mercury in the body over time.
More specifically, fishes like swordfish, king mackerel and shark are known to concentrate higher amount of mercury than other species of fishes. Hence, limiting their consumption will protect humans from mercury poisoning.
The correct option is b.
