Question

1- How many moles of N2O5 contain the same number of nitrogen atoms as exactly 19 mol of NO2?

2- How many grams are contained in 0.900 mol of calcium phosphate, Ca3 (PO4)2?

3- Ga

Number of electrons =_______ electrons

Number of protons = _________protons

4- element number 79

Number of electrons = _____electrons

Number of protons = ______protons

5- What are the symbol and name for an element whose average atoms have a mass that is 59.6% of the mass of an average chromium atom?

Symbol:

Name:

6- In the first 36 elements, 8 elements have atoms whose average mass is within 0.2 u of being twice the atomic number of the element. Choose the symbols and names for these 8 elements.

(Select all that apply.)

- oxygen

-silicon

-chlorine

-helium

-bromine

-sulfur

-boron

-argon

-aluminum

-carbon

-lithium

-calcium

-nitrogen

-neon

-copper

-sodium

Answer 1

1)

for number of Nitrogen atom to be same, number of mol of Nitrogen atom should also be same

19 mol of NO2 has 19 moles of N

So, N2O5 should also have 19 moles of N

Since 1 mol of N2O5 has 2 mol of N

moles of N2O5 = 19/2 = 9.5 moles

Answer: 9.5 moles

2)

Molar mass of Ca3(PO4)2,

MM = 3*MM(Ca) + 2*MM(P) + 8*MM(O)

= 3*40.08 + 2*30.97 + 8*16.0

= 310.18 g/mol

mass of Ca3(PO4)2,

m = number of mol * molar mass

= 0.9 mol * 310.18 g/mol

= 279 g

Answer: 279 g

I am allowed to answer only 1 question at a time