Question

part i: balance the following equations by adding coefficients in the blanks.

1. what are the steps for balancing a chemical equation?

a. write un - balanced (skeleton) equation
b. count atoms of each element
c. adjust coefficients
d. verify final equation

1. 2mg + __o₂→2mgo
2. cucl₂ + h₂s→cus + hcl

part ii: determine the unknown amount of a substance in a chemical reaction.

1. 40 g of calcium reacts with 71 g of chlorine to produce __ g of calcium chloride.
2. __ g of potassium reacts with 16 g of oxygen to produce 94 g of potassium oxide.
3. 14 g of lithium reacts with __ g sulfur to produce 46 g of lithium sulfide.
4. 24 g of magnesium reacts with 38 g of fluorine to produce __ g magnesium fluoride.

Explanation:

Step1: Recall law of conservation of mass

In a chemical reaction, mass is conserved. The total mass of reactants equals the total mass of products.

Step2: Answer question 1

The steps for balancing a chemical equation are: write the un - balanced equation, count atoms of each element, adjust coefficients, verify final equation.

Step3: Balance equation in question 2

The balanced equation is $2Mg + O_2
ightarrow2MgO$, so the coefficient for $O_2$ is 1.

Step4: Balance equation in question 3

The balanced equation is $CuCl_2 + H_2S
ightarrow CuS+2HCl$, so the coefficients are 1, 1, 1, 2.

Step5: Solve question 4

According to the law of conservation of mass, $40 + 71=111$ g of calcium chloride is produced.

Step6: Solve question 5

Let the mass of potassium be $x$. By the law of conservation of mass, $x + 16=94$, so $x = 94 - 16=78$ g.

Step7: Solve question 6

Let the mass of sulfur be $y$. By the law of conservation of mass, $14 + y=46$, so $y = 46 - 14 = 32$ g.

Step8: Solve question 7

By the law of conservation of mass, $24+38 = 62$ g of magnesium fluoride is produced.

Answer:

1. Write un - balanced equation, count atoms of each element, adjust coefficients, verify final equation
2. 1
3. 1, 1, 1, 2
4. 111
5. 78
6. 32
7. 62