What is the molar mass of Na2Cr2O7?

Calculate number of grams in 1.15*10^21 molecules of P2O5

Vlada [557]

To go from molecules, we first need to convert to moles and then convert to grams.

To convert from molecules to moles, we need to divide by Avogadro's constant.

1.15*10^21 molecules * (1 mole/6.022*10^23 molecules) = 0.0019097 moles

To convert from moles to grams, we need to use the molar mass.

The molar mass of P₂O₅ is (2*30.98)+(5*16.00) = 141.96
You can find the molar mass using the periodic table.

0.0019097 moles * (141.96 grams/1 mole) = 0.2711 grams.

Since we have 3 significant digits in 1.15*10^21, that means our final answer is limited to 3 significant digits.

Your final answer is 0.271 grams.

6 0

4 years ago

What is the molar concentration of Cu2+ in a solution that is labelled 5 ppm Cu2+? a)7.9x10^(-5)M b)7.9x10^(-6)M c)5.1x10^(-6)M

Savatey [412]

Answer:

1.24x10⁻⁴ mol/L

Something went wrong with the choices

Explanation:

5 ppm is a sort of concentration that indicates:

weigh of solute x 10⁶ / weigh of solution or volume of solution.

Relation must be in the order of 10⁻⁶, for example mg/kg / μg/g.

We can also write ppm as μg/mL, so 5 ppm will be understood as 5 μg of Ca²⁺ in 1mL of solution.

This would be the rule of three to reach molarity

In 1mL we have 5 μg of Ca²⁺

In 1000 mL we would have 5000 μg of Ca²⁺

Let's convert 5000 μg to g ( 1g = 1x10⁶μg)

5000 μg = 5x10⁻³ g

Now, that we have the mass, we convert it to moles (mass / molar mass)

5x10⁻³ g / 40.08g/m = 1.24x10⁻⁴ moles

As this moles are in 1000mL (1L) it's molarity

5 0

3 years ago

How do i write a c-e-r for this

Maurinko [17]

Answer: it’s B for edge !

Explanation: took the test

4 0

3 years ago

When 16 g of methane (CH4) and 32 g of oxygen (O2) reacted to produce carbon dioxide and water, 11 g of carbon dioxide was produ

Aliun [14]

Answer:

Percent yield = 50%

Explanation:

Given data:

Mass of CH₄ = 16 g

Mass of O₂ = 32 g

Mass of CO₂ = 11 g

Percent yield of CO₂ = ?

Solution:

Chemical equation:

CH₄ + 2O₂ → CO₂ + 2H₂O

Number of moles of CH₄:

Number of moles = mass/ molar mass

Number of moles = 16 g /16 g/mol

Number of moles = 1 mol

Number of moles of O₂:

Number of moles = mass/ molar mass

Number of moles = 32 g /32 g/mol

Number of moles = 1 mol

Now we will compare the moles of CO₂ with both reactant.

O₂ : CO₂

2 : 1

1 : 1/2×1= 0.5 mol

CH₄ : CO₂

1 : 1

Number of moles of CO₂ produced by oxygen are less so it will limiting reactant.

Theoretical yield:

Mass of CO₂:

Mass = number of moles × molar mass

Mass = 0.5 mol × 44 g/mol

Mass = 22 g

Percent yield:

Percent yield = actual yield / theoretical yield × 100

Percent yield = 11 g/ 22 g × 100

Percent yield = 50%

3 0

3 years ago

How many different principal quantum numbers can be found in the ground-state electron configuration of nickel?A) 2.B) 3.C) 4.D)

Naddik [55]

Answer:

C) 4.

Explanation:

Hello!

In this case, since the electron configuration of nickel at its ground-state, considering 28 as its atomic number and the number of electrons it has in one atom, is:

$Ni^{28}:1s^2,2s^2,2p^6,3s^2,3p^6,4s^2,3d^8$

We can see it has four energy levels, 1, 2, 3 and 4, which are related to the following principal quantum number, that describes the energy of an electron in the atom and its most probable distance with respect to the nucleus.

Therefore, nickel has C) 4 different principal quantum numbers.

Best regards!

5 0

3 years ago