Question

1.)If you are given the number of particles in a substance sample, what is the first step you should take to determine how many grams are present in that sample?

Find the molar mass of the substance.

Convert the grams to particles.

Convert the moles to mass.

Convert the number of particles to moles.


2.)Phosphoric acid, which is a component of many soft drinks, has a molar mass of 98.00 grams per mole. A sample of phosphoric acid contains 3.1 percent hydrogen, 31.6 percent phosphorus, and 65.3 percent oxygen by mass. What is the molecular formula of phosphoric acid?

HPO

H2PO2

H3PO4

H6P2O8


3.)Which of the following cannot occur in a chemical reaction?

New atoms are created.

Heat is released.

Light is produced.

Temperature is changed.


4.)What information do the coefficients in a balanced chemical equation tell you?

The amount of energy from the products.

The ratios of the number of moles of each substance that react and that are produced.

The physical states of the compounds reacting.

The elements involved in the reaction.


5.)Which law states that, in chemical reactions, the total mass of reactants must equal the total mass of the products?

conservation of molecules

conservation of energy

conservation of mass

conservation of elements


6.)How do you know if an equation is balanced?

All substances in the equation have written coefficients.

The reactant and product coefficient totals are equal.

The number of atoms for every element is equal on both sides of the equation.

All coefficients are divisible by two.


7.)In a reaction, 15 moles of carbon dioxide are produced from 5 moles of iron (III) oxide and 15 moles of carbon monoxide. What is the mole ratio of carbon dioxide to carbon monoxide?

15:5

5:15

1:3

1:1


8.)What is the mole ratio of C3H8 to carbon dioxide in the following equation?

C3H8 + 5O2 à 3CO2 + 4H2O

3:03

11:06

1:03

24:06:00


9.)Two moles of hydrogen gas is reacted with oxygen gas to produce water in this reaction:

2 H2 + O2 → 2 H2O

In the lab you actually made 33.1 grams of water. What is the percent yield?

108.10%

91.80%

5.50%

100%

Answer 1

To determine the number of grams in a substance sample, you first need to find its molar mass. Once the molar mass is known, you can convert the number of particles to moles and then to grams using the molar mass.

Step-by-step explanation:

The first step to determine the number of grams in a substance sample, given the number of particles, is to find the molar mass of the substance. The molar mass is the mass in grams of one mole of representative particles of that substance. Once the molar mass is known, the number of particles can be converted to moles and then to grams using the molar mass as a conversion factor.

Answer 2

1-Find the molar mass of the substance.

2-H3PO4

3-New atoms are created.

4-The ratios of the number of moles of each substance that react and that are produced.

5-conservation of mass

6-The number of atoms for every element is equal on both sides of the equation.

7-1:1

8-1:03

9-5.50%