What electrons participate in chemical bonding?

The amount ofcalcium present in milk can be determined by adding oxalate to asample and measuring the massof calcium oxalate pre

Sauron [17]

Answer: The mass percent of calcium in milk is 0.107 %

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ .....(1)

Given mass of calcium oxalate = 0.429 g

Molar mass of calcium oxalate = 128.1 g/mol

Putting values in equation 1, we get:

$\text{Moles of calcium oxalate}=\frac{0.429g}{128.1g/mol}=0.0033mol$

The given chemical equation follows:

$Na_2C_2O_4(aq.)+Ca^{2+}(aq.)\rightarrow CaC_2O_4(s)+2Na^+(aq.)$

Sodium oxalate is present in excess. So, it is considered as an excess reagent. And, calcium ion is a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

1 mole of calcium oxalate is produced from 1 mole of calcium ion

So, 0.0033 moles of calcium oxalate is produced from = $\frac{1}{1}\times 0.0033=0.0033mol$ of calcium ions

Now, calculating the mass of calcium ions by using equation 1, we get:

Moles of calcium ions = 0.0033 moles

Molar mass of calcium ions = 40 g/mol

Putting values in equation 1, we get:

$0.0033mol=\frac{\text{Mass of calcium ions}}{40g/mol}\\\\\text{Mass of calcium ions}=(0.0033mol\times 40g/mol)=0.132g$

To calculate the mass percentage of calcium ions in milk, we use the equation:

$\text{Mass percent of calcium ions}=\frac{\text{Mass of calcium ions}}{\text{Mass of milk}}\times 100$

Mass of milk = 125 g

Mass of calcium ions = 0.132 g

Putting values in above equation, we get:

$\text{Mass percent of calcium ions}=\frac{0.132g}{125g}\times 100=0.107\%$

Hence, the mass percent of calcium in milk is 0.107 %

7 0

3 years ago

The Ksp can be used to find the concentration of hydroxide ions, and thus determine the pH given a concentration of of aluminum.

Anton [14]

Answer:

3.9.

Explanation:

(Molar mass of 342.15 g/mol).

The first thing to do in this question is to coverts our units. We are given 6.70 lb = 453.592 × 6.70 lb = 3039.0664 g of aluminum sulfate.

2050 gallons of water = 2050 × 3.785 = 7759.25 Litres.

After this we will now look for the Concentration aluminum sulfate using the formula below:

Concentration = number of moles ÷ volume. ------------------------------------(1).

Recall; Number of moles = 3039.0664/ 342.15 = 8.8823 moles. The volume = 2050 gallons = 7759.25 Litres.

Therefore, slotting in the values of of number of moles and volume into the equation (1) above, we have;

Concentration= 8.8823 moles/ 7759.25 Litres. = 0.001145 M.

The next equation we are going to make use of today is that of the solubilty product that is;

Ksp = (Al^3+) (OH^-)^3.

So, we have the ksp = 1.3 × 10^-33 and the value of (Al^3+)= 0.001145 M.

Hence, making (OH^-) the subject of the formula;

(OH^-) = ( 1.3 × 10^-33 / 0.001145)^1/3.

(OH^-) = 8 × 10^-11 M.

Hence, pOH = - log (OH^-)

pOH = - log (8 × 10^-11).

pOH = 10.1

Therefore, the values of pH is; 1

pH + pOH = 14.

pH = 14 - 10.1 = 3.9.

3 0

4 years ago

Which statements describe an element? Check all that apply.

Molodets [167]

Answer:

Hello, Your answer will be B,C,E, And F.

Explanation:

An element is a substance whose atoms have same number of protons which means all atoms in an element have same atomic number. Elements are simplest substances which cannot be broken down by physical changes or chemical reactions. Elements are classified by their names and symbols. Hope That Helps!

8 0

4 years ago

A ground state hydrogen atom absorbs a photon of light having a wavelength of 92.05 nm. It then gives off a photon having a wave

vodka [1.7K]

Absorbed photon energy
Ea = hc/λ.. (Planck's equation)
Ea = hc / 92.05^-9m

Energy emitted
Ee = hc/ 1736^-9m 

Energy retained ..
∆E = Ea - Ee = hc(1/92.05^-9 - 1/1736^-9) 
∆E = (6.625^-34)(3.0^8) (1.028^7)
∆E = 2.04^-18 J 

Converting J to eV (1.60^-19 J/eV)
∆E = 2.04^-18 / 1.60^-19
∆E = 12.70 eV 

Ground state (n=1) energy for Hydrogen = - 13.60eV 

New energy state = (-13.60 + 12.70)eV = -0.85 eV 

Energy states for Hydrogen
En = - (13.60 / n²) 

n² = -13.60 / -0.85 = 16
n = 4

4 0

3 years ago

Write a net ionic equation for the overall reaction that occurs when aqueous solutions of sodium hydroxide and hydrosulfuric aci

Helga [31]

Answer:

2OH-(aq) + 2H+(aq) → 2H2O(l)

Explanation:

Step 1: Data given

sodium hydroxide = NaOH

hydrosulfuric acid = H2S

Step 2: The unbalanced equation

NaOH(aq) + H2S(aq) → Na2S(aq) + H2O(l)

Step 3: Balancing the equation

On the left side we have 1x Na (in NaOH), on the right side we have 2x Na (in Na2S). To balance the amount of Na on both sides, we have to multiply NaOH on the left side by 2.

2NaOH(aq) + H2S(aq) → Na2S(aq) + H2O(l)

On the left side we have 4x H (2x in NaOH and 2x in H2S), on the right side we have 2x H (in H2O). To balance the amount of H on both sides, we have to multiply H2O on the right side by 2. Now the equation is balanced.

2NaOH(aq) + H2S(aq) → Na2S(aq) + 2H2O(l)

Step 4: The net ionic equation

2Na+(aq) + 2OH-(aq) + 2H+(aq) + S^2-(aq) → 2Na+(aq) + S^2-(aq) + 2H2O(l)

The net ionic equation, for which spectator ions are omitted - remember that spectator ions are those ions located on both sides of the equation - will , after canceling those spectator ions in both side, look like this:

2OH-(aq) + 2H+(aq) → 2H2O(l)

8 0

4 years ago