Question

To determine the formula of a new substance, one of the first steps is to find the ____. A. molar mass B. percent composition C. volume at STP D. number of particles per mole

Answer 1

The correct option is B.

To determine the formula of a new substance, one has to first determine the percentage composition of each of the elements in the compound. The ratios of each element in the compound will give information about how much of each element is present. The formula of the element will be given based on the quantity of each constituent in the compound.

Answer 2

One of the steps in the determination of the formula of a new substance is $\boxed{{\text{B}}{\text{. percent composition}}}$.

Further explanation:

Empirical formula:

It is atom’s simplest positive integer ratio in the compound. It may or may not be the same as that of molecular formula. For example, empirical formula of carbon dioxide is CO.

Molecular formula:

It is a chemical formula that indicates total number and kinds of atoms in molecule. For example, molecular formula of carbon dioxide is ${\text{C}}{{\text{O}}_2}$.

Step 1: The percentage composition of each element present in the compound is to be determined. This is done by considering the total percentage of the compound to be 100 %.

Step 2: The mass of each element is to be calculated. This is done using equation (1).

The formula to calculate the mass of the element is as follows:

${\text{Mass of element}}=\left({\frac{{{\text{Element \% }}}}{{{\text{100 \% }}}}} \right)\left({{\text{Mass of compound}}}\right)$          …… (1)

Step 3: The number of moles of each element is to be calculated. This is done using equation (2).

The formula to calculate the moles of each element is as follows:

${\text{Moles of element}}=\frac{{{\text{Given mass of element}}}}{{{\text{Molar mass of element}}}}$                  …… (2)

Step 4: The preliminary formula of the compound is to be formed. This is done by dividing the moles of each element by the smallest number of moles.

Step 5: The empirical formula of the compound is to be formed.

So percent composition is one of the steps that are required to determine the formula of a new substance and therefore option B is correct.

Learn more:

1. Calculate the moles of ions in the solution: https://brainly.com/question/5950133

2. Calculate the moles of chlorine in 8 moles of carbon tetrachloride: https://brainly.com/question/3064603

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Stoichiometry of formulas and equations

Keywords: empirical formula, molecular formula, preliminary formula, CO, CO2, moles, compound, element, percent composition, correct, B, mass of element, mass of compound.