Question

"Na2SO3” represents sodium sulfite.

What does the 4 mean in the formula 4Na2SO3?

There are four atoms of sodium.
There are four atoms of sodium sulfite.
There are four molecules of sodium sulfite.
There are four elements in sodium sulfite.



Which gas law describes the relationship between temperature and pressure at a constant volume?

Boyle’s law
Charles’s law
Gay-Lussac’s law
combined gas law




The descriptions below explain two ways that water is used by plants on a sunny day.

I. In a process called transpiration, some liquid water in leaves changes to water vapor. The water vapor is released into the air through tiny pores in the leaves. This allows more liquid water from the soil to be pulled up the roots and stem to replace water lost from the leaves.

II. Plants use some of this water in leaves in a process called photosynthesis. During photosynthesis, water and carbon dioxide break apart and recombine to form two new substances, oxygen and glucose.

Based on the above description of transpiration and photosynthesis, which type of change happens to water during each process?

In transpiration, because some of its properties change, water undergoes a physical change but keeps its identity. In photosynthesis, because its identity changes, water undergoes a chemical change.
In transpiration, because some of its properties change, water undergoes a chemical change but keeps its identity. In photosynthesis, because its identity changes, water undergoes a physical change.
In transpiration, because its physical properties change, water undergoes a physical change and loses its identity. In photosynthesis, because it keeps its identity, water undergoes a chemical change.
In transpiration, because its chemical properties change, water undergoes a chemical change and loses its identity. In photosynthesis, because it keeps its identity, water undergoes a physical change.



Which refers to the type of chemical bond that involves the transfer of electrons between atoms?

metallic
polar covalent
ionic
covalent

Answer 1

1) 4Na2SO3 — Answer: There are four molecules (or formula units) of sodium sulfite.
- The 4 is a coefficient meaning four units of Na2SO3 (each unit contains 2 Na, 1 S, 3 O).

2) Gas law relating temperature and pressure at constant volume — Answer: Gay-Lussac’s law.
- At constant volume, pressure is directly proportional to temperature.

3) Transpiration vs photosynthesis — Answer:
- Transpiration: physical change (phase change from liquid to vapor, identity of H2O unchanged).
- Photosynthesis: chemical change (water molecules are chemically transformed into new substances).

4) Bond type involving transfer of electrons — Answer: ionic.