Question

how many moles of ammonia are there in a 346 g sample of pure nh3?
o c.20.3 mol
o a.0.0496 mol
o d.5930 mol
o b.24.7 mol

question 6
how many atoms of calcium are there in 25.0 g of calcium chloride?
o b.2.71x10^23 atoms
o c.2.67x10^24 atoms
o a.1.36x10^23 atoms
o d.1.95x10^23 atoms

question 7
a new element has the symbol y and seven valence electrons. what is the maximum number of hydrogen atoms that can bond to y?
o d.7
o a.1
o b.4
o c.3

question 8
what is name of the following compound nh4no3?
o d.ammonium nitrate
o c.nitrogen hydride nitrite
o b.ammonium nitrite
o a.ammonia nitrite

Explanation:

Step1: Calculate molar mass of NH₃

The molar mass of N is 14.01 g/mol and H is 1.01 g/mol. For NH₃, molar mass $M = 14.01+3\times1.01=17.04$ g/mol.

Step2: Calculate moles of NH₃

Using the formula $n=\frac{m}{M}$, where $m = 346$ g and $M = 17.04$ g/mol. So $n=\frac{346}{17.04}\approx20.3$ mol.

Step1: Calculate molar mass of CaCl₂

The molar mass of Ca is 40.08 g/mol, Cl is 35.45 g/mol. For CaCl₂, $M=40.08 + 2\times35.45=110.98$ g/mol.

Step2: Calculate moles of CaCl₂

Using $n=\frac{m}{M}$, with $m = 25.0$ g and $M = 110.98$ g/mol, so $n=\frac{25.0}{110.98}\approx0.225$ mol.

Step3: Determine moles of Ca

In 1 mole of CaCl₂, there is 1 mole of Ca. So moles of Ca is also 0.225 mol.

Step4: Calculate number of Ca atoms

Using Avogadro's number $N = n\times N_A$, where $N_A=6.022\times 10^{23}$ atoms/mol. So $N=0.225\times6.022\times 10^{23}\approx1.36\times 10^{23}$ atoms.

An atom with 7 valence - electrons needs 1 more electron to complete its octet. Hydrogen has 1 valence electron. So the maximum number of hydrogen atoms that can bond to Y is 1.

The compound NH₄⁺ is ammonium ion and NO₃⁻ is nitrate ion. So the name of NH₄NO₃ is ammonium nitrate.

Answer:

c. 20.3 mol