Physical Science A Mod 5

In the compound 3Ca₃(PO₄)₂, how many atoms of oxygen are there?

• 4

• 8

• 16

• 24

Answer explanation

In 3Ca₃(PO₄)₂, there are 2 phosphate (PO₄) groups. Each phosphate has 4 oxygen atoms, totaling 8 oxygen atoms per formula unit. With 3 formula units, the total is 3 x 8 = 24 oxygen atoms.

Tags

NGSS.MS-PS1-1

Which of the following is the correct count of atoms for the compound Al₂(SO₄)₃?

• Al=1, S=2, O=6

• Al=2, S=3, O=12

• Al=2, S=1, O=4

• Al=3, S=2, O=6

Answer explanation

In Al₂(SO₄)₃, there are 2 aluminum (Al), 3 sulfur (S), and 12 oxygen (O) atoms. The sulfate ion (SO₄) has 4 oxygen atoms, and with 3 sulfate ions, it totals 12 oxygen atoms. Thus, the correct count is Al=2, S=3, O=12.

Tags

NGSS.MS-PS1-1

What is the molar mass of Sn (Tin)?

• 39.10 g/mol

• 207.2 g/mol

• 118.71 g/mol

• 78.96 g/mol

Answer explanation

The molar mass of Tin (Sn) is 207.2 g/mol, which is the correct choice among the options provided. This value is based on the atomic weight of Tin found on the periodic table.

What is the numerical value of Avogadro's number?

• 1.23 x 10²³

• 3.14 x 10²³

• 6.022 x 10²³

• 9.81 x 10²³

Answer explanation

Avogadro's number, which is the number of particles in one mole of a substance, is defined as 6.022 x 10²³. This value is fundamental in chemistry for converting between moles and number of atoms or molecules.

Tags

NGSS.HS-PS1-7

Which type of reaction is represented by the equation 2 HgO → 2 Hg + O₂?

• Synthesis

• Single-Replacement

• Double-Replacement

• Decomposition

Answer explanation

The reaction 2 HgO → 2 Hg + O₂ involves the breakdown of mercury(II) oxide into mercury and oxygen. This is characteristic of a decomposition reaction, where a single compound breaks down into two or more products.

According to the law of conservation of mass, if 8 grams of CH₄ react completely with 32 grams of O₂, how many grams of products are formed?

• 40 grams

• 32 grams

• 24 grams

• 16 grams

Answer explanation

According to the law of conservation of mass, the total mass of reactants equals the total mass of products. Here, 8 grams of CH₄ and 32 grams of O₂ react to form 40 grams of products (8g + 32g = 40g).

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Balance the following equation: Fe₂O₃ + H₂ → Fe + H₂O

• Fe₂O₃ + 6 H₂ → 2 Fe + 6 H₂O

• Fe₂O₃ + 3 H₂ → 2 Fe + 3 H₂O

• 2 Fe₂O₃ + 6 H₂ → 4 Fe + 3 H₂O

• 2 Fe₂O₃ + 6 H₂ → 4 Fe + 6 H₂O

Answer explanation

To balance the equation, we need 3 H₂ for every Fe₂O₃ to produce 2 Fe and 3 H₂O. Thus, the balanced equation is Fe₂O₃ + 3 H₂ → 2 Fe + 3 H₂O, making this the correct choice.

Tags

NGSS.MS-PS1-5

Which type of reaction is represented by the equation Cu + 2AgNO₃ → 2Ag + Cu(NO₃)₂?

• Combustion

• Decomposition

• Single-Replacement

• Double-Replacement

Answer explanation

The reaction Cu + 2AgNO₃ → 2Ag + Cu(NO₃)₂ is a Single-Replacement reaction. Here, copper (Cu) replaces silver (Ag) in silver nitrate (AgNO₃), forming silver (Ag) and copper(II) nitrate (Cu(NO₃)₂).

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

In an endothermic reaction, what happens to energy?

• It is released to the surroundings.

• It is absorbed from the surroundings.

• It remains constant.

• It decreases the mass of the products.

Answer explanation

In an endothermic reaction, energy is absorbed from the surroundings to break bonds in the reactants, leading to a decrease in temperature of the surroundings. Thus, the correct choice is that energy is absorbed.

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5

Which factor would generally decrease the rate of a chemical reaction?

• Adding a catalyst

• Increasing the temperature

• Increasing the surface area

• Decreasing the concentration of reactants

Answer explanation

Decreasing the concentration of reactants reduces the number of particles available to collide, which generally slows down the reaction rate. In contrast, adding a catalyst, increasing temperature, or surface area would increase the rate.

Tags

NGSS.HS-PS1-5