Unit 14 Practice Test*

Front

What is the formula to calculate the percentage composition of an element in a compound?

Back

Percentage composition = (mass of element in 1 mole of compound / molar mass of compound) x 100

Front

What is the molar mass of Magnesium Oxide (MgO)?

Back

The molar mass of MgO is 40.305 g/mol.

Front

How do you calculate the number of moles from grams?

Back

Number of moles = mass (g) / molar mass (g/mol).

Front

What is the molar mass of Iron(II) Chloride (FeCl2)?

Back

The molar mass of FeCl2 is approximately 126.75 g/mol.

Front

How many molecules are in one mole of a substance?

Back

One mole of any substance contains approximately 6.022 x 10^23 molecules (Avogadro's number).

Front

What is the relationship between moles and molecules?

Back

Moles are a measure of quantity in chemistry, while molecules are the actual particles. 1 mole = 6.022 x 10^23 molecules.

Front

How do you convert grams to moles?

Back

To convert grams to moles, divide the mass of the substance by its molar mass.

Front

What is the significance of Avogadro's number in chemistry?

Back

Avogadro's number (6.022 x 10^23) allows chemists to count particles by weighing them.

Front

What is the formula for calculating the number of moles of a gas at standard temperature and pressure (STP)?

Back

At STP, 1 mole of gas occupies 22.4 liters.

Front

How do you find the empirical formula from percent composition?

Back

Convert percent to grams, divide by molar mass to find moles, and then simplify the ratio.