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15,739 solutions

Mole Concept

Q. How many mmol of iron are there in 650 mg of iron? A. 11.6 mmol Fe B. 363.02 mmol Fe C. 55.85 mmol Fe D. 8.95 mmol Fe

Solved • Feb 24, 2020

Mole Concept

Q. How many atoms (total) are there in one formula unit of Ca3(PO4)2?

Solved • Feb 24, 2020

First Order Half Life

Q. Tritium (3H) is used in glowing “EXIT” signs located where there is no electricity for lightbulbs. If the half-life of tritium is 12.26 years, what percentage of the original quantity of the isotope is left in the sign after 20.0 years? a.0.677%. d.32.3%. b.67.7%. e.25.0%. c.0.323%

Solved • Feb 25, 2020

Empirical Formula

Q. A chloride of rhenium contains 63.6% rhenium. What is the formula of this compound? A. ReCl7 B. ReCl C. ReCl5 D. Re2Cl3 E. ReCl3

Solved • Feb 24, 2020

Molarity

Q. A 165.0 mL solution of 2.878 M strontium nitrate is mixed with 220.0 mL of a 3.338 M sodium fluoride solution. Calculate the mass of the resulting strontium fluoride precipitate. Assuming complete precipitation, calculate the final concentration of each ion. If the ion is no longer in solution, enter a 0 for the concentration.

Solved • Feb 24, 2020

Mole Concept

Q. Calculate the mass in grams of 86.551 mol of Na 2HPO4.7H2O. (Example answer: 123.4) Do not enter units with your answer.

Solved • Feb 24, 2020

Isotopes

Q. Silicon, which makes up about 25% of Earth's crust by mass, is used widely in the modern electronics industry. It has three naturally occurring isotopes, 28-Si, 29-Si, and 30-Si. Calculate the atomic mass of silicon. A. 29.2252 amu B. 28.9757 amu C. 28.7260 amu D. 28.0855 amu E. 27.9801 amu

Solved • Feb 24, 2020