For a good quality of cement, ratio of lime (CaO) to total of oxide of silicon `(SiO_2)`, aluminium `(Al_2O_3)` and iron `(Fe_2O_3)` should be as close to

Options

A. 2
B. 3
C. 4
D. 5

Answer

To determine the ratio of lime (CaO) to the total of the oxides of silicon (SiO2), aluminum (Al2O3), and iron (Fe2O3) for good quality cement, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Components**:
- The main components of cement include:
- Calcium Oxide (CaO) - Lime
- Silicon Dioxide (SiO2) - Silicon oxide
- Aluminum Oxide (Al2O3) - Aluminum oxide
- Iron Oxide (Fe2O3) - Iron oxide

2. **Understand the Composition**:
- For good quality cement, the typical composition percentages are:
- CaO: 50-60%
- SiO2: 20-25%
- Al2O3: 5-10%
- Fe2O3: 1-2%

3. **Calculate the Total of SiO2, Al2O3, and Fe2O3**:
- To find the total of SiO2, Al2O3, and Fe2O3, we can take an average of their percentage ranges:
- SiO2 = 22.5% (average of 20-25%)
- Al2O3 = 7.5% (average of 5-10%)
- Fe2O3 = 1.5% (average of 1-2%)
- Total = SiO2 + Al2O3 + Fe2O3 = 22.5% + 7.5% + 1.5% = 31.5%

4. **Determine the Ratio of CaO to Total Oxides**:
- If we take the average percentage of CaO as 55% (between 50-60%), we can now find the ratio:
- Ratio of CaO to total oxides = CaO / (SiO2 + Al2O3 + Fe2O3)
- Ratio = 55% / 31.5%

5. **Calculate the Ratio**:
- To simplify the ratio, we can convert percentages to a ratio:
- Ratio = 55 / 31.5 = 1.746 (approximately 2 when rounded)

6. **Conclusion**:
- Therefore, the ratio of lime (CaO) to the total of the oxides of silicon (SiO2), aluminum (Al2O3), and iron (Fe2O3) should be as close to **2** for good quality cement.

### Final Answer:
The ratio of lime (CaO) to the total of the oxides of silicon (SiO2), aluminum (Al2O3), and iron (Fe2O3) should be as close to **2**.