Fossil evidence indicates that the following events occurred in what sequence, from earliest to most recent?

1. Protostomes invade terrestrial environments.

2. Cambrian explosion occurs.

3. Deuterostomes invade terrestrial environments.

4. Vertebrates become top predators in the seas.

#Question id: 391

#XL - S Microbiology

In a hospital laboratory, a 10.0 mL sample of gastric juice, obtained several hours after a meal, was titrated with 0.1 M NaOH to neutrality; 7.2 mL of NaOH was required. The patient’s stomach contained no ingested food or drink, thus assume that no buffers were present. What was the pH of the gastric juice?

#Question id: 392

#XL - S Microbiology

When an ionic compound such as sodium chloride (NaCl) is placed in water, the component atoms of the NaCl crystal dissociate into individual sodium ions (Na+) and chloride ions (Cl-). In contrast, the atoms of covalently bonded molecules (e.g., glucose, sucrose, glycerol) do not generally dissociate when placed in aqueous solution. Which of the following solutions would be expected to contain the greatest number of solute particles (molecules or ions)?

#Question id: 394

#XL - S Microbiology

What will be the H+ ion concentration in a solution prepared by mixing 50.0 mL of 0.20 M NaCl, 25 mL of 0.10M NaOH and 25.0 mL of 0.30M HCl?

#Question id: 395

#XL - S Microbiology

How would acidification of seawater affect marine organisms? Acidification of seawater would ________.

#Question id: 399

#XL - S Microbiology

Calculate the pH of a 1 L solution containing 0.100 M formic acid and 0.100 M sodium formate before and after the addition of 1.00 mL of 5.00 M NaOH. How much would the pH change if the NaOH were added to 1.00 L of pure water? (pKa for formic acid is 3.75)

#Question id: 400

#XL - S Microbiology

Consider two solutions: solution X has a pH of 4; solution Y has a pH of 7. From this information, we can reasonably conclude that ________.