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3 years ago

A salt crystal has a mass of 0.17 mg . how many nacl formula units does it contain?

1 answer:

7 0

1. Calculate the mass of the formula unit (fu). Na= 22.990 g/mol Cl= 35.453 g/mol so total = 22.990 g/mol + 35.453 g/mol = 58.443 g/mol 1 mol = 6.02 x10^23 formula units, so (58.443 g/mol)*(1 mol/6.02x10^23 fu)= 9.7x10^-23 2. Convert mass to grams: (0.17 mg)*(1 g/1000 mg) = 0.00017 g 3. Calculate number of formula units: 0.00017 g x (1 fu/9.7x10^-23 g) = 1.8x10^18 Or more simply: (.00017 g) * (1 mol/58.443 g) * (6.02x10^23 fu/1mol) = 1.8x10^18

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Urea makes up a significant amount of urine, and is the chemical that the body uses to rid cells of unwanted carbon dioxide and

Ira Lisetskai [31]

Urea is highly soluble in water. When it is allowed to dissolve in water in the presence of heat, it will yield ammonia and carbon dioxide. The reaction is shown below:

NH2-CO-NH2 + H2O ⇒ 2 NH3 + CO2

As you can observe in the stoichiometric equations, 1 molecule of water can dissolve with 1 mole of urea.

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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

Zn + O2= ZnO How many moles of zinc are needed to make 500. g of zinc oxide?

s2008m [1.1K]

Answer:

5.15 moles

Explanation:

2zn + o2 = 2zno

5.15 2.57 5.15 moles

nzno=500/(16x2+65)= 5.15 moles

-> nzn = 5.15 x 2 ÷ 2 = 5.15 moles

6 0

3 years ago

Element Q has an atomic number 68. Consider the isotope Q-136 how many protons are in a neutral atom of this isotope?

mote1985 [20]

Answer: 68

Explanation:

Isotopes of an element have same number of protons but different number of neutrons. Which means isotopes of an element have same atomic number but different mass number.

Atomic number is equal to the number of protons or the number of electrons for a neutral atom and is specific to a particular element.

Mass number is the sum of number of protons and the number of neutrons.

Given : atomic number of element Q = 68 = number of protons

Mass number of isotope Q-136 = 136

But as isotopes have same atomic number, the number of protons will be same and hence there are 68 protons are in a neutral atom of this isotope.

7 0

3 years ago

Is frictional force desirable?

gavmur [86]

Answer: Friction is a force that resists relative motion between two surfaces in contact. Depending on the application, friction may be desirable or undesirable.

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3 years ago