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lorasvet [3.4K]
3 years ago
9

Which best describes the act of using senses or tools to gather information? creating a hypothesis making an observation summari

zing the results recording the measurements
Chemistry
1 answer:
MAXImum [283]3 years ago
3 0

Answer:

making an observation

Explanation:

its the right answer

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A student is investigating the effect of concentration on the colour of a solution of copper sulfate.She wished to make up 250cm
IrinaK [193]

Answer:

79.8g/dm³

Explanation:

As you can see, the solution in the problem contains 0.5 moles of copper sulfate per dm³. To solve this question we must convert these moles to grams using its molar mass (Molar mass CuSO4 = 159.609g/mol) as follows:

0.5mol CuSO4/dm³ * (159.609g/mol) =

<h3>79.8g/dm³</h3>
3 0
2 years ago
An original sample of the radioisotope fluorine-21 had a mass of 80.0 milligrams. Only 20.0 milligrams of this original sample r
lyudmila [28]

<u>Answer:</u> The correct answer is Option 3.

<u>Explanation:</u>

All the radioisotope decay processes follow first order kinetics.

Rate law expression for first order kinetics is given by the equation:

k=\frac{2.303}{t}\log\frac{a}{a-x}

where,  

k = rate constant  = ?

t = time taken for decay process = 8.32 seconds

a = initial amount of the reactant  = 80 mg

a - x = amount left after decay process  = 20 mg

Putting values in above equation, we get:

k=\frac{2.303}{8.32sec}\log\frac{80g}{20}\\\\k=0.166sec^{-1}

The equation used to calculate half life for first order kinetics:

t_{1/2}=\frac{0.693}{k}

where,

t_{1/2} = half life of the reaction = ?

k = 0.166sec^{-1}

Putting values in above equation, we get:

t_{1/2}=\frac{0.693}{0.166sec^{-1}}=4.16sec

Hence, the correct answer is Option 3.

5 0
2 years ago
Read 2 more answers
Calculate the partial pressure of each gas and the total pressure if the temperature of the gas is 21 ∘C∘C. Express the pressure
Volgvan

The question is incomplete, complete question is ;

A deep-sea diver uses a gas cylinder with a volume of 10.0 L and a content of 51.8 g of O_2 and 33.1 g of He. Calculate the partial pressure of each gas and the total pressure if the temperature of the gas is 21°C.Express the pressures in atmospheres to three significant digits separated by commas.

Answer:

Partial pressure of the oxygen gas is 3.91 atm.

Partial pressure of the helium gas is 20.0 atm

Total pressure of the gases is 24.0 atm

Explanation:

Moles of oxygen gas = n_1=\frac{51.8}{32 g/mol}=1.619 mol

Moles of helium gas = n_2=\frac{33.1 g}{4 g/mol}=8.275 mol

Total moles of gas = n_1+n_2=(1.619 +8.275 ) mole=9.894 mol

Volume of the cylinder = V = 10.0 L

Total pressure in the cylinder = P = ?

Temperature of the gas in cylinder = T = 21°C = 21 + 273 K = 294 K

PV = nRT ( ideal gas equation )

P=\frac{nRT}{V}

=\frac{9.894 mol\times 0.0821 atm L/mol K\times 294 K}{10.0 L}

P = 23.88 atm ≈ 23.9

Partial pressure of the individual gas will be determined by the help of Dalton's law:

partial pressure = Total pressure × mole fraction of gas

Partial pressure of the oxygen gas

p_{1}=P\times \chi_{1}=P\times \frac{n_1}{n_1+n_2}

p_1=23.88 atm\times \frac{1.619 mol}{9.894 mol}=3.91 atm

Partial pressure of the helium gas

p_{2}=P\times \chi_{2}=P\times \frac{n_2}{n_1+n_2}

p_2=23.88 atm\times \frac{8.275 mol}{9.894 mol}=19.97 atm\approx 20.0 atm

6 0
3 years ago
What is a valence electron and why are they so important to a chemist?
Reika [66]
They are important because they are the electrons that help the atom to bond with another atom. They are in the outer most shell. ☺️
3 0
2 years ago
What is the solution to the problem expressed to the correct number of significant figures?
Lena [83]

Answer:

B

Explanation:

3 0
2 years ago
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