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SCORPION-xisa [38]
3 years ago
15

PLEASE HELP this is chemistry 12 points

Chemistry
1 answer:
Inessa05 [86]3 years ago
8 0

Answer:

6.791

Explanation:

For proper significant figures with addition, you would use the significant figures of the number with lowest decimal place.  6.298 goes to the 10⁻³ place.  0.492712 goes to the 10⁻⁶ place.  You will go out to the 10⁻³ place.

6.298 + 0.492712 = 6.790712 ≈ 6.791

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17 p<br> 18 n<br> What is the atomic number of this element?
Verdich [7]

Answer:

Chlorine

Explanation:

The P usually stands for Protons, and that is usually the element number. (chlorine is 17) N is for neutron

6 0
3 years ago
What is the molecular formula of a compound with an empirical formula P2O5 and a gram-molecular mass of 284 grams? And why?
Lana71 [14]
I really don’t know but

Phosphorus pentoxide is a white solid which does not have any distinct odour. The chemical formula of this compound is P4O10. However, it is named after its empirical formula, which is P2O5. The molar mass of phosphorus pentoxide corresponds to 283.9 g/mol.
5 0
3 years ago
The equilibrium concentrations of the reactants and products are [ HA ] = 0.260 M [HA]=0.260 M , [ H + ] = 2.00 × 10 − 4 M [H+]=
ValentinkaMS [17]

Answer:

pKa of the acid HA with given equilibrium concentrations is 6.8

Explanation:

The dissolution reaction is:

HA ⇔ H⁺ + A⁻

So at equilibrium, Ka is calculated as below

Ka = [H⁺] x [A⁻] / [HA] = 2.00 x 10⁻⁴ x 2.00 x 10⁻⁴ / 0.260

    = 15.38 x 10⁻⁸

Hence, by definition,

pKa = -log(Ka) = - log(15.38 x 10⁻⁸) = 6.813

7 0
3 years ago
LIMITING REACTANT!! Please help I’m very confused.
alexira [117]

Answer:

We'll have 1 mol Al2O3 and 3 moles H2

Explanation:

Step 1: data given

Numer of moles of aluminium = 2 moles

Number of moles of H2O = 6 moles

Step 2: The balanced equation

2Al + 3H2O → Al2O3 + 3H2

Step 3: Calculate the limiting reactant

For 2 moles Al we need 3 moles H2O to produce 1 mol Al2O3 and 3 moles H2

Aluminium is the limiting reactant. It will completely be consumed (2 moles).

H2O is in excess. There will react 3/2 * 2 = 3 moles

There will remain 6 - 3 = 3 moles

Step 4: Calculate moles products

For 2 moles Al we need 3 moles H2O to produce 1 mol Al2O3 and 3 moles H2

For 2 moles Al we'll have 2/1 = 1 mol Al2O3

For 2 moles Al We'll have 3/2 * 2 = 3 moles H2

We'll have 1 mol Al2O3 and 3 moles H2

8 0
4 years ago
What is earth's crust mainly composed of ​
____ [38]

Answer:

The crust is made of solid rocks and minerals. Beneath the crust is the mantle, which is also mostly solid rocks and minerals, but punctuated by malleable areas of semi-solid magma. At the center of the Earth is a hot, dense metal core.

Explanation:

5 0
3 years ago
Read 2 more answers
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