Question

1. what is the mass of 8.12 × 10²³ molecules of co₂ gas? (atomic mass of carbon = 12.011 u; oxygen = 15.999 u.)

○ 32.6 g
○ 44.0 g
○ 48.9 g
○ 59.3 g

1. sulfuric acid (h₂so₄) has a molar mass of 98.1 g/mol. how many oxygen atoms are found in 75.0 g of h₂so₄?

○ 1.15 × 10²³
○ 1.84 × 10²⁴
○ 4.61 × 10²³
○ 7.87 × 10²³

Explanation:

Step1: Calculate the number of moles of \(CO_2\)

Use Avogadro's number \(N = 6.022\times10^{23}\text{mol}^{-1}\). The number of moles \(n\) of \(CO_2\) is \(n=\frac{N_{molecules}}{N_A}\), where \(N_{molecules}=8.12\times 10^{23}\). So \(n=\frac{8.12\times 10^{23}}{6.022\times10^{23}\text{mol}^{-1}}\approx1.35\text{mol}\)

Step2: Calculate the molar mass of \(CO_2\)

The molar mass \(M\) of \(CO_2\) is \(M=(12.011 + 2\times15.999)\text{g/mol}=44.009\text{g/mol}\approx44.0\text{g/mol}\)

Step3: Calculate the mass of \(CO_2\)

Use the formula \(m = n\times M\). Substitute \(n = 1.35\text{mol}\) and \(M = 44.0\text{g/mol}\). Then \(m=1.35\text{mol}\times44.0\text{g/mol}=59.4\text{g}\approx59.3\text{g}\) (due to rounding differences in intermediate steps)

Answer:

59.3 g