Which chemicals are known to raise pH in water?

The choice that identifies the chemicals known to raise pH in water includes soda ash (sodium carbonate) and caustic soda (sodium hydroxide). Both of these substances are alkaline, meaning they can increase the pH level of water when added.

Soda ash is commonly used in water treatment processes to neutralize acidity and stabilize pH levels. It effectively responds to excess hydrogen ions (H+) in the water, thereby increasing the pH. Similarly, caustic soda is a strong base that significantly raises pH levels upon dissolving in water, making it a common choice for raising alkalinity in water treatment applications.

In contrast, the other options contain either acidic or neutral substances that do not contribute to raising pH. This is why the selection of soda ash and caustic soda is particularly relevant for applications requiring an elevation of pH.