All categories

3 years ago

PLEASE HELP!!

2 answers:

ivann1987 [24]3 years ago

5 0

The half-life of a radioactive substance describes the amount of time required for half of that radioactive substance to decay into a different form.

In this situation, 100 grams decays into 12.5 grams over the course of 8 hours. We have half lives that look like this -

100 grams - 50 grams (1) - 25 grams (2) - 12.5 grams (3)

three half lives have passed since the start over the course of eight hours, so:

8 hours/3 half-lives = ~2.667 hours per half-life

The half-life of this substance is approximately 2.667 hours.

Hope this helps!

omeli [17]3 years ago

3 0

Answer:

8/3 hours

Explanation:

12.5/100=1/8, 1/8*2=2/8=1/4 1/4*2=1/2 1/2*2 = 1 (whole)

we multiplyed 1/8 by two three times to get 1 so 8/3 hours is the answer

by the way i'm in 6th grade

You might be interested in

Given the balanced equation:

Marta_Voda [28]

The answer is (2) A bond is formed and energy is released. The left side of equation is I atom and the right side of equation is I2 molecule. So the bond is formed between I atom to form I2 molecule. And forming bond will release energy while breaking bond will absorb energy.

7 0

3 years ago

Qu 4.

Anna11 [10]

Answer:

It's the second one down.

Explanation:

Gold

Mass 197

Number of Protons: 79

Number of Neutrons: 197 - 79 = 118

Number of electrons: = number of protons = 97

3 0

2 years ago

A serving of soup contains 5.0 g of fat, 20.0 g of carbohydrates, and 3.0 g of protein. Determine how many kilocalories (kcal) a

marta [7]

Answer: The amount of kilocalories contained in the given serving of soup is 0.137 kCal

Explanation:

As per the USDA:

Carbohydrates provide 4 calories per gram, protein provides 4 calories per gram, and fat provides 9 calories per gram.

We are given

Mass of fat in the soup serving = 5.0 g

Mass of carbohydrates in the soup serving = 20.0 g

Mass of protein in the soup serving = 3.0 g

Conversion factor used: 1 kCal = 1000 Cal

Applying unitary method:

For Fat:

1 gram of fat provides 9 calories

So, 5.0 gram of fat will provide = $\frac{9}{1}\times 5.0=45Cal=0.045kCal$

For Carbohydrates:

1 gram of carbohydrates provides 4 calories

So, 20.0 gram of carbohydrates will provide = $\frac{4}{1}\times 20.0=80Cal=0.080kCal$

For Proteins:

1 gram of proteins provides 4 calories

So, 3.0 gram of fat will provide = $\frac{4}{1}\times 3=12Cal=0.012kCal$

Total kilocalories per serving = [0.045 + 0.080 + 0.012] kCal = 0.137 kCal

Hence, the amount of kilocalories contained in the given serving of soup is 0.137 kCal

4 0

3 years ago

Please help me with these questions I don't get science

LiRa [457]

Proteins are made of carbon, hydrogen,oxygen, and nitrogen (CHON). Nucleic acids such as DNA and RNA contain carbon,hydrogen, oxygen, nitrogen, and phosphorus(CHON P). The body also needs trace amounts of other elements such as calcium,potassium, and sulfur for proper functioning of muscles, nerves, etc.

4 0

2 years ago

Read 2 more answers

2A + B + 2C ? D + E

Amanda [17]

Answer:

C Rate $=k [A]^{2} [B][C]^{-1}$

Explanation:

In order to determine the correct rate law, let's use Trial 1 as baseline. Therefore:

An increase in [A] in Trial 2 by a factor of $\sqrt{2}$ leads to an increase in the rate of reaction by a factor of 2 (i.e. the reaction rate is doubled). Thus, there is second order in [A].

Similarly,

An increase in [B] in Trial 3 by a factor of 1.667 leads to an increase in the rate of reaction by a factor of 1.667. Thus, there is first order in [B].

Futhermore,

An increase in [C] in Trial 4 by a factor of 1.71 leads to a decrease in the rate of reaction by 1.71. Thus, there is inverse first order in [C].

Therefore, the correct rate law is:

Rate $=k [A]^{2} [B][C]^{-1}$

8 0

2 years ago