APES UCLA MATH

An atom has 25 protons, 30 neutrons, and 25 electrons. What is the charge of the atom's nucleus?

• +25
• +30
• -25
• -30

A transfer of energy involves three steps, each of which is 80% efficient.  What is the approximate total efficiency of all three steps?

• 66%
• 51%
• 24%
• 80%

A population takes about seven years to double in size.  This population annual percentage growth is approximately

• 2%
• 7%
• 10%
• 15%

Tags

NGSS.HS-LS2-2

A population experienced a birth rate of 23 people per thousand and a death rate of 11 deaths per thousand.  What is the approximate growth rate of the population?

• 2.4%
• 1.2%
• 3.8%
• 0.12%

Tags

NGSS.HS-LS2-2

. Radioactive I-131 has a half-life of 8 days.  How much time is required for a millicurie sample of I-131 to decay to an activity of 1 microcurie?

• about 3 months
• about a year
• 16 days
• about 1 month

An adult takes 400 mg of ibuprofen. Each hour, the amount of ibuprofen in the person’s system decreases by about 20%. How much ibuprofen is left after 4 hours? 

• 205 mg
• 256
• 320 mg
• 164mg

What is Half-life?

• The amount of time it takes for some of the nuclei in a sample of the isotope to decay
• The amount of time it takes for half the electrons in a sample of the isotope to decay
• The amount of time it takes for half the nuclei in a sample of the isotope to decay
• the amount of time it takes to double the nuclei in a sample of the isotope to decay

After the third half-life, how much of the sample is left?

• 1/2
• 1/3
• 1/16
• 1/8

Barium-122 has a half-life of 2 minutes. A fresh sample weighing 80 g was obtained. If it takes 10 minutes to set up an experiment using barium-122, how much barium-122 will be left when the experiment begins?

• 0.25g
• 2.5g
• 25g
• 80g

How many protons does U 235 atom have ?

• 235
• 92
• 143
• 67