3.Un trozo de hierro de 50 gramos se calienta a \( 100^{\circ} \mathrm{C} \) y luego se pone en agua fria, donde su emperatura baja a \( 30^{\circ} \mathrm{C} \) ¿Cuantas calorias cede el hierro al egua? (Ce s \( \mathrm{e}^{\left.-0.11 \mathrm{cal} / \mathrm{g}^{\circ} \mathrm{C}\right)} \)

A chemist carefully measures the amount of heat needed to raise the temperature of a 197.0 g sample of a pure substance from \( 49.4^{\circ} \mathrm{C} \) to \( 67.7^{\circ} \mathrm{C} \). The experiment shows that 16.9 kJ of heat are needed. What can the chemist report for the specific heat capacity of the substance? Be sure your answer has the correct number of significant digits.

If 82 g of sugar is dissolved in 7950 mL of water, what is the concentration of the solution?

A partir de la siguiente ecuación de combustión de octano, si reaccionan 59.2 gramos de octano, ¿Cuántos gramos de Oxígeno se necesitan? \[ \mathrm{C}_{8} \mathrm{H}_{18}+25 / 2 \mathrm{O}_{2}-->8 \mathrm{CO}_{2}+9 \mathrm{H}_{2} \mathrm{O} \] Considera: \( \mathrm{C}: 12, \mathrm{O}: 16, \mathrm{H}: 1 \)

При образовании 2,2г СО \( { }_{2} \) по уравнению реакции: \( \mathrm{C}(\mathrm{тв})+\mathrm{O}_{2}=\mathrm{CO}_{2}(\mathrm{r}) \) выделилось 19,7 кДж теплоты. Стандартная энтальпия образования \( \mathrm{CO}_{2}(\mathrm{r}) \) в кДж/ моль равна -197 +394 +197 \( -394 \times \)

A formula connecting density \( (d) \), mass \( (m) \) and volume \( (v) \) is \[ d=\frac{m}{v} \] \( m=30.14 \mathrm{~g} \) after being truncated to 2 d.p. \( v=3.78 \mathrm{~cm}^{3} \) after being truncated to 2 d.p. Calculate the lower and upper bounds of \( d \). Round your answers to \( 2 \mathrm{~d} . \mathrm{p} \).