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Fed [463]
2 years ago
5

What is not a guideline required for a valid evidence test?

Chemistry
1 answer:
kirill115 [55]2 years ago
4 0
I just took that quiz , it’s A
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Lt takes 4 hr 39 min for a 2.00-mg sample of radium-230 to decay to 0.25 mg. what is the half-life of radium-230?
Rufina [12.5K]
Radioactive decay => C = Co { e ^ (- kt) |

Data:

Co = 2.00 mg
C = 0.25 mg
t = 4 hr 39 min

Time conversion: 4 hr 39 min = 4.65 hr

1) Replace the data in the equation to find k

C = Co { e ^ (-kt) } => C / Co = e ^ (-kt) => -kt = ln { C / Co} => kt = ln {Co / C}

=> k = ln {Co / C} / t =  ln {2.00mg / 0.25mg} / 4.65 hr = 0.44719

2) Use C / Co  = 1/2 to find the hallf-life

C / Co = e ^ (-kt) => -kt = ln (C / Co)

=> -kt = ln (1/2) => kt = ln(2) => t = ln (2) / k

t = ln(2) / 0.44719 = 1.55 hr.

Answer: 1.55 hr
6 0
3 years ago
A Snickers bar contains 27.0 g of sugars (carbohydrates), 4.0 g of protein and 12.0 g of fat. How many food calories (Cal) are c
amm1812

Answer:

There are 232 calories in the bar

Explanation:

Carbohydrates and protein are both 4 calories per gram, while fat is 9 calories per gram.

27*4=108\\4*4=16\\12*9=108\\108+108+16=232

4 0
2 years ago
Which of the following statements is a true statement regarding a solution with [H1+] =1x10-5 M and [OH1-]= 1x10-9 M?
zheka24 [161]

Answer:

B. The [H1+] >[OH1-] and the solution is acidic

4 0
2 years ago
A sample of oxygen gas occupies 3.60 liters at a pressure of 1.00 atm. If temperature is held constant, what will be the volume
Soloha48 [4]

Answer: The volume of the oxygen gas at a pressure of 2.50 atm will be 1.44 L

At constant temperature, the volume of a fixed mass of gas is inversely proportional to the pressure it exerts, then

PV = c

Thus, if the pressure increases, the volume decreases, and if the pressure decreases, the volume increases.

It is not necessary to know the exact value of the constant c to be able to use this law since for a fixed amount of gas at constant temperature, it is satisfied that,

P₁V₁ = P₂V₂

Where P₁ and P₂ as well as V₁ and V₂ correspond to pressures and volumes for two different states of the gas in question.

In this case the first oxygen gas state corresponds to P₁ = 1.00 atm and V₁ = 3.60 L while the second state would be P₂ = 2.50 atm and V₂ = y. Substituting in the previous equation,

1.00 atm x 3.60 L = 2.50 atm x y

We cleared y to find V₂,

V₂ = y = \frac{1.00 atm x 3.60 L}{2.50 atm} = 1.44 L

Then, <u>the volume of the oxygen gas at a pressure of 2.50 atm will be 1.44 L</u>

3 0
3 years ago
Determine molar mass! help please
bezimeni [28]

Answer:

the molar mass is the mass of a given chemical element or chemical compound divided by the amount of substance

8 0
2 years ago
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