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प्रश्न
Heshna and Keerthi are friends. Keerthi’s teeth are white without caries, but Heshna has teeth with caries. Why? How is it formed?
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उत्तर
- Caries are caused by the action of acids on the enamel surface.
- The acid is produced when sugar in foods or drinks reacts with bacteria present on the tooth surface.
- Heshna has not cleaned her teeth well after sipping sugary drinks and snacking.
- She has to brush after meals and before bed.
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संबंधित प्रश्न
Name an indicator which is pink in alkaline solution but turns colourless in acidic solution.
The indicator which produces a pink colour in an alkaline solution is:
(a) methyl orange
(b) turmeric paper
(c) phenolphthalein
(d) litmus paper
The salt which will give a neutral solution on dissolving in water will be:
(a) CH3COONa
(b) NH4Cl
(c) KCl
(d) Na2CO3
If iron reacts with dilute sulphuric acid, what will be the products?
The word sour refers to ______ in Latin.
Fill in the missing data in the following table
| Name of the salt | Formula | Salt obtained from | ||
| Base | Acid | |||
| (i) | Ammonium chloride | NH4Cl | NH4OH | ______ |
| (ii) | Copper sulphate | ______ | ______ | H2SO4 |
| (iii) | Sodium chloride | NaCl | NaOH | ______ |
| (iv) | Magnesium nitrate | Mg(NO3)2 | ______ | HNO3 |
| (v) | Potassium sulphate | K2SO4 | ______ | ______ |
| (vi) |
Calcium nitrate | Ca(NO3)2 | Ca(OH)2 | ______ |
Which of the following metal does not react with sodium hydroxides?
Complete the following equation.
HCl + H2O → ______ + ______.
Complete the following equation.
H+ + H2O → ______.
Complete the following equation.
CaO + H2SO4 → ______ + H2O
