Question

1. which atomic particle is directly involved in chemical reactions?

a. neutron
b. proton
c. electron
d. nucleon

1. 6 g of sugar is dissolved in 250ml of water. what is the percent concentration of sugar in mass per unit

volume?
a. 2.4%
b. 0.024%
c. 60%
d. 6%

1. on the periodic table, carbon is atomic number 6 and has an atomic mass of 12.0 amu. how many sub-

atomic particles are found in the nucleus of a carbon atom?
a. 2
b. 8
c. 12
d. 16

1. the reactant that is completely used up is called the ---------.

a. reactant
b. limiting reactant
c. halved
d. excess

1. a person starts a fire in a fire pit. he burns the wood in the pit to ashes. this burning of the wood has

caused the wood to change from on substance (wood) to another substance (ashes)
this change from one substance to another substance is called what?
a. physical change
b. ionic change
c. chemical change
d. material change

1. which of the following numbers contains the designated correct number of significant figures?

a. 0.04300 5 significant figures
b. 0.00302 2 significant figures
c. 156 000 3 significant figures
d. 1.04 2 significant figures
page 5 of 6

1. the following graph shows how the concentration (amount per unit volume) changes with time.

what information can be obtained from the data?
concentration of a reactant
as a function of time
0.20
0.15
0.10
0.05
0.00
0 100 200 300 400 500 600
time (seconds)
a. the amount of reactant does not change with time.

Explanation:

Question 17

In chemical reactions, electrons are involved in forming bonds (transfer or sharing). Neutrons and protons are in the nucleus, and nucleons (protons + neutrons) don't participate directly in reactions. So electrons are the particles involved.

Step1: Recall the formula for mass/volume percent concentration

The formula is $\text{Percent concentration} = \frac{\text{mass of solute}}{\text{volume of solution}} \times 100\%$. Here, solute is sugar (6 g), solution volume is 250 mL (since water is the solvent, and we assume volume of solution ≈ volume of solvent for dilute solutions).

Step2: Substitute values into the formula

$\text{Percent concentration} = \frac{6\ \text{g}}{250\ \text{mL}} \times 100\% = \frac{6}{250} \times 100 = 2.4\%$.

Step1: Recall sub - atomic particles in the nucleus

The nucleus of an atom contains protons and neutrons. These are called nucleons. Atomic number (Z) is the number of protons, and atomic mass (A) is the sum of protons and neutrons. For carbon, atomic number (Z) = 6 (protons), atomic mass (A) = 12.0 amu. So number of neutrons (n) = A - Z = 12 - 6 = 6.

Step2: Calculate total sub - atomic particles in the nucleus

Total nucleons (protons + neutrons) in the nucleus = 6 (protons) + 6 (neutrons) = 12.

Answer:

C. Electron

Question 18