@media (max-width: 767px) {
  .back-to-top {
    bottom: 10rem !important;
    right: 1.5rem !important;
    z-index: 998 !important;
  }
  
  /* Caso o botão tenha outra classe */
  .btn-back-to-top, 
  .voltar-topo,
  .scroll-top {
    bottom: 10rem !important;
    right: 1.5rem !important;
    z-index: 998 !important;
  }
}