Some Basic Conc...

What could be better than a dozen $$(12)$$ donuts? How about a baker's dozen $$(13)$$ of donuts? Another large unit of measurement is known as Avogadro's number $$(6.022\times 10^{23})$$.
What is TRUE about Avogadro's number?

How many molecules of water are present in a $$0.25\ mole$$ of $$H_2O$$?

What is the mass of $$6.022\times { 10 }^{ 23 }$$ molecules of $${NH}_{3}$$?

What is the mass of $$6.022\times { 10 }^{ 23 }$$ formula units of $${({NH}_{4})}_{2}{SO}_{4}$$?

Referring to the molecular sketch and table above, choose the option that best describes the percentage of carbon in the molecule, in terms of both atomic composition and mass-percent composition.

The atomic mass of copper is $$64\ amu$$, while the atomic mass of oxygen is $$16\ amu$$.
Let $$= copper$$ and $$= oxygen$$.
Which of the following would represent a compound that was $$50$$% copper, by mass?

Consider the figure below, in which the blue circles represent atoms of copper metal, atomic mass $$63.5\ amu$$, while the red circles represent atoms in zinc metal, atomic mass $$65.4\ amu$$.
Here are four statements concerning this system. Identify the correct statement or statements.
I. This is a single-phase mixture, with a copper-to-zinc atom ratio of $$3 : 1$$.
II. This is two-phase mixture, with a copper-to-zinc atom ratio of $$8 : 1$$.
III. The mixture is $$80$$% copper, by mass.
IV. This mixture could be an alloy of copper and zinc.

How many molecules of methane are present in a sample that contains $$1.0\times { 10 }^{ 10 }$$ moles of methane?

Equal masses of oxygen, hydrogen, and methane are taken in a container in identical condition. Find the ratio of volumes of the gases.

How many grams of $$CaWO_4$$ would contain the same mass of tungsten that is present in 569g of $$FeWO_4$ $? (W=184)