Is sidewalk cement an element or a compound?

98 ! and brainliest plz ! the below reaction can be categorized as more than one type of reaction. which reactions are these, and what are the types of reactions?

When the chemicals iron sulfide (fes) and hydrochloric acid (hcl) are combined, bubbles appear from the mixture. 1. does the appearance of bubbles indicate a physical or chemical change? 2. why do the bubbles indicate this change? 3. what property is this?

2ki + pb(no3)2 → 2kno3 + pbi2 determine how many moles of kno3 are created if 0.03 moles of ki are completely consumed.