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2 years ago

Humans have used rocks in the creation of tools and building materials true or flase

Chemistry

2 answers:

olga55 [171]2 years ago

8 0

Answer:

true

Explanation:

Anuta_ua [19.1K]2 years ago

4 0

True, if you would like an example look at Indian arrow heads or early architecture all use rocks.

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Explain how the removal of thermal energy (heat) from matter affects its particles

den301095 [7]

Answer:

You can change an object's state of matter by adding or removing thermal energy. When you add thermal energy to an object, these things can happen: Particles move faster

Explanation:

6 0

2 years ago

What is the mass in grams of 0.280 mole sample of sodium hydroxide NaOH

vivado [14]

Answer:

The mass of 0.280 mole sample of sodium hydroxide NaOH is 11.2 grams.

Explanation:

To know the mass in grams of 0.280 moles of sample of sodium hydroxide NaOH, you must know the molar mass of the compound, that is, the mass of one mole of a substance, which can be an element or a compound.

So you know:

Na: 23 g/mole
O: 16 g/mole
H: 1 g/mole

So, the molar mass of NaOH is:

NaOH= 23 g/mole + 16 g/mole+ 1 g/mole= 40 g/mole

Then the following rule of three can be applied: if in 1 mole of sodium hydroxide there are 40 grams, in 0.280 moles how much mass is there?

$mass=\frac{0.28 moles*40 grams}{1 mole}$

mass= 11.2 grams

The mass of 0.280 mole sample of sodium hydroxide NaOH is 11.2 grams.

4 0

2 years ago

Why do we need to use moles when we try to determine amounts of reactants and products in a reaction?.

ICE Princess25 [194]

$\huge\fbox{Answer ☘}$

Chemists use the mole unit to represent 6.022 × 10 23 things, whether the things are atoms of elements or molecules of compounds. This number, called Avogadro's number, is important because this number of atoms or molecules has the same mass in grams as one atom or molecule has in atomic mass units.

hope helpful~

8 0

2 years ago

Which of the following does NOT play a role in South Florida’s climate?

Arlecino [84]

Answer:

i think a im not sure

Explanation:

4 0

2 years ago

The powder mixture (Cu, Al and Fe) = 10g was oxidized from sufficient chloride acid. 1) What are the possible reactions to the p

Mandarinka [93]

Answer:

1) 2Al + 6HCl ⟶ 2AlCl₃ + 3H₂

Fe + 2HCl ⟶ FeCl₂ + H₂

2) Cu = 2.5 g; Al = 3.5 g; Fe = 4.0 g

Explanation:

1) Possible reactions

2Al + 6HCl ⟶ 2AlCl₃ + 3H₂

Fe + 2HCl ⟶ FeCl₂ + H₂

2) Mass of each metal

a) Mass of Cu

The waste was the unreacted copper.

Mass of Cu = 2.5 g

b) Masses of Al and Fe

We have two relations :

Mass of Al + mass of Fe = 10 g - 2.5 g = 7.5 g

H₂ from Al + H₂ from Fe = 6.38 L at NTP

i) Calculate the moles of H₂

NTP is 20 °C and 1 atm.

$\begin{array}{rcl}pV & = & n RT\\\text{1 atm} \times \text{6.38 L} & = & n \times 0.08206 \text{ L}\cdot\text{atm}\cdot\text{K}^{-1}\text{mol}^{-1} \times \text{293.15 K}\\6.38 & = & 24.06n \text{ mol}^{-1} \\n & = & \dfrac{6.38}{24.06 \text{ mol}^{-1} }\\\\ & = & \text{0.2652 mol}\\\end{array}$

(ii) Solve the relationship

Let x = mass of Al. Then

7.5 - x = mass of Fe

Moles of Al = x/27

Moles of Fe = (7.5 - x)/56

Moles of H₂ from Al = (3/2) × Moles of Al = (3/2) × (x/27) = x /18

Moles of H₂ from Fe = (1/1) × Moles of Fe = (7.5 - x)/56

∴ x/18 + (7.5 - x)/56 = 0.2652

56x + 18(7.5 - x) = 267.3

56x + 135 - 18x = 267.3

38x = 132.3

x = 3.5 g

Mass of Al = 3.5 g

Mass of Fe = 7.5 g - 3.5 g = 4.0 g

The masses of the metals are Cu = 2.5 g; Al = 3.5 g; Fe = 4.0 g

4 0

3 years ago