When an acid reacts with a carbonate or metal hydrogen, it forms salts, carbon dioxide gas and water accordingly. Which of the following equations is correct for this chemical reaction?
Na₂CO₃(s) + HCl(aq) → 2NaCl(aq) + H₂O(l) + 2CO₂(g) + H₂O(l)
Na₂CO₃(s) + HCl(aq) → NaCl(aq) + H₂O(l) + CO₂(g)
Na₂CO₃(s) + 2HCl(aq) → 2NaCl(aq) + H₂O(l) + CO₂(g)
Na₂CO₃(s) + 2HCl(aq) → 2NaCl(aq) + 2CO₂(g)
The table below shows the passing percentage of four schools in four years.
| Name of school | 2012-13 | 2013-14 | 2014-15 | 2015-16 |
| PQR | 27% | 31% | 45% | 67% |
| ABC | 61% | 65% | 50% | 78% |
| DEF | 95% | 86% | 80% | 70% |
| XYZ | 92% | 82% | 78% | 71% |
The percentage of which school is increasing sequentially (gradually)?
The elevation angle of the tower is 30° from the 18 m high top of a platform. If the height of the tower is 78 m, then what is the distance of the tower from the platform?